[2420] fixed old memory datasrc test failed to prevent failure due to singonly

this is an intermediate regression due to the previous change.  It's an ugly
workaround, but the real fix is to deprecate the old version ASAP, so I
didn't bother to fix it cleanly.

src/lib/datasrc/tests/memory_datasrc_unittest.cc

@@ -1219,7 +1219,7 @@ TEST_F(InMemoryZoneFinderTest, loadFromIterator) {
     // purpose of this test, so it should just succeed.
     db_client = unittest::createSQLite3Client(
         class_, origin_, TEST_DATA_BUILDDIR "/contexttest.sqlite3.copied",
-        TEST_DATA_DIR "/contexttest.zone");
+        TEST_DATA_DIR "/contexttest-almost-obsolete.zone");
     zone_finder_.load(*db_client->getIterator(origin_));
 
     // just checking a couple of RRs in the new version of zone.

src/lib/datasrc/tests/testdata/contexttest-almost-obsolete.zone

@@ -0,0 +1,85 @@
+;; test zone file used for ZoneFinderContext tests.
+;; RRSIGs are (obviouslly) faked ones for testing.
+
+example.org. 3600 IN SOA	ns1.example.org. bugs.x.w.example.org. 78 3600 300 3600000 3600
+example.org.			      3600 IN NS	ns1.example.org.
+example.org.			      3600 IN NS	ns2.example.org.
+example.org.			      3600 IN RRSIG	NS 7 3 3600 20150420235959 20051021000000 40430 example.org. FAKEFAKEFAKE
+example.org.			      3600 IN MX	1 mx1.example.org.
+example.org.			      3600 IN MX	2 mx2.example.org.
+example.org.			      3600 IN MX	3 mx.a.example.org.
+
+ns1.example.org.		      3600 IN A		192.0.2.1
+ns1.example.org.		      3600 IN RRSIG	A 7 3 3600 20150420235959 20051021000000 40430 example.org. FAKEFAKE
+ns1.example.org.		      3600 IN AAAA	2001:db8::1
+ns1.example.org.		      3600 IN RRSIG	AAAA 7 3 3600 20150420235959 20051021000000 40430 example.org. FAKEFAKEFAKE
+ns2.example.org.		      3600 IN A		192.0.2.2
+ns2.example.org.		      3600 IN TXT	"text data"
+
+mx1.example.org.		      3600 IN A		192.0.2.10
+mx2.example.org.		      3600 IN AAAA	2001:db8::10
+
+;; delegation
+a.example.org.			      3600 IN NS	ns1.a.example.org.
+a.example.org.			      3600 IN NS	ns2.a.example.org.
+a.example.org.			      3600 IN NS	ns.example.com.
+
+ns1.a.example.org.		      3600 IN A		192.0.2.5
+ns2.a.example.org.		      3600 IN A		192.0.2.6
+ns2.a.example.org.		      3600 IN AAAA	2001:db8::6
+mx.a.example.org.		      3600 IN A		192.0.2.7
+
+;; delegation, one of its NS names is at zone cut.
+b.example.org.			      3600 IN NS	ns.b.example.org.
+b.example.org.			      3600 IN NS	b.example.org.
+b.example.org.			      3600 IN AAAA	2001:db8::8
+
+ns.b.example.org.		      3600 IN A		192.0.2.9
+
+;; The MX name is at a zone cut.  shouldn't be included in the
+;; additional section.
+mxatcut.example.org.		      3600 IN MX	1 b.example.org.
+
+;; delegation, one of its NS names is under a DNAME delegation point;
+;; another is at that point; and yet another is under DNAME below a
+;; zone cut.
+c.example.org. 	      	      3600 IN NS	ns.dname.example.org.
+c.example.org. 	      	      3600 IN NS	dname.example.org.
+c.example.org.      	      3600 IN NS	ns.deepdname.example.org.
+ns.dname.example.org.		      3600 IN A		192.0.2.11
+dname.example.org.		      3600 IN A		192.0.2.12
+ns.deepdname.example.org.	      3600 IN AAAA	2001:db8::9
+
+;; delegation, one of its NS name is at an empty non terminal.
+d.example.org. 	      	      3600 IN NS	ns.empty.example.org.
+d.example.org. 	      	      3600 IN NS	ns1.example.org.
+;; by adding these two we can create an empty RB node for
+;; ns.empty.example.org in the in-memory zone
+foo.ns.empty.example.org.     3600 IN A		192.0.2.13
+bar.ns.empty.example.org.     3600 IN A		192.0.2.14
+
+;; delegation; the NS name matches a wildcard (and there's no exact
+;; match).  One of the NS names matches an empty wildcard node, for
+;; which no additional record should be provided (or any other
+;; disruption should happen).
+e.example.org. 	      	      3600 IN NS	ns.wild.example.org.
+e.example.org. 	      	      3600 IN NS	ns.emptywild.example.org.
+e.example.org. 	      	      3600 IN NS	ns2.example.org.
+*.wild.example.org.	      3600 IN A		192.0.2.15
+a.*.emptywild.example.org.    3600 IN AAAA	2001:db8::2
+
+;; additional for an answer RRset (MX) as a result of wildcard
+;; expansion
+*.wildmx.example.org. 3600 IN MX 1 mx1.example.org.
+
+;; the owner name of additional for an answer RRset (MX) has DNAME
+dnamemx.example.org. 3600 IN MX 1 dname.example.org.
+
+;; CNAME
+alias.example.org. 3600 IN CNAME cname.example.org.
+
+;; DNAME
+dname.example.org. 3600 IN DNAME dname.example.com.
+
+;; DNAME under a NS (strange one)
+deepdname.c.example.org. 3600 IN DNAME deepdname.example.com.