tests: Distribute virnetserverdata

Fairly recently we've introduced virnetservertest. This test has some
input data stored under tests/virnetserverdata which unfortunately was
not distributed among with the test. Therefore 'make distcheck'
failed. Fix this by adding the directory into EXTRA_DIST.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

tests/Makefile.am

@@ -138,6 +138,7 @@ EXTRA_DIST =		\
 	vircgroupdata \
 	virfiledata \
 	virnetdevtestdata \
+	virnetserverdata \
 	virpcitestdata \
 	virscsidata \
 	virusbtestdata \