[master] use install-sh (with -m) instead of cp to make sure writable test

DB file has write permission.  hopefully it should fix the distcheck failure
on the freebsd8 buildbot.

src/lib/datasrc/tests/testdata/Makefile.am

@@ -1,5 +1,6 @@
 CLEANFILES = *.copied
 BUILT_SOURCES = rwtest.sqlite3.copied
 
+# We use install-sh with the -m option to make sure it's writable
 rwtest.sqlite3.copied: $(srcdir)/rwtest.sqlite3
-	cp $(srcdir)/rwtest.sqlite3 $@
+	$(top_srcdir)/install-sh -m 644 $(srcdir)/rwtest.sqlite3 $@