tests: Fix incorrect check for virNetServerClientClose call

Commit id '6df5d777' somehow during the move from one branch to
another added an erroneous '!'...
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

tests/virnetserverclienttest.c

@@ -152,7 +152,7 @@ static int testIdentity(const void *opaque ATTRIBUTE_UNUSED)
     ret = 0;
  cleanup:
     virObjectUnref(sock);
-    if (!client)
+    if (client)
         virNetServerClientClose(client);
     virObjectUnref(client);
     virObjectUnref(ident);