rpc: remove redundant logic

Introduced by commit <0eaa59dc>.  That comparison already returns
true or false.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

src/rpc/virnetserverclient.c

@@ -1090,7 +1090,7 @@ virNetServerClientClose(virNetServerClientPtr client)
 bool
 virNetServerClientIsClosedLocked(virNetServerClientPtr client)
 {
-    return client->sock == NULL ? true : false;
+    return client->sock == NULL;
 }