remove useless target in Makefile which just use for testing

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/trac397focused@3860 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/datasrc/Makefile.am

@@ -14,4 +14,4 @@ libdatasrc_la_SOURCES += static_datasrc.h static_datasrc.cc
 libdatasrc_la_SOURCES += sqlite3_datasrc.h sqlite3_datasrc.cc
 libdatasrc_la_SOURCES += query.h query.cc
 libdatasrc_la_SOURCES += cache.h cache.cc
-libdatasrc_la_SOURCES += rbtree.h rbtree.cc
+libdatasrc_la_SOURCES += rbtree.h