rpc: avoid double close on error

Spotted by coverity.  If pipe2 fails, then we attempt to close
uninitialized fds, which may result in a double-close.

* src/rpc/virnetserver.c (virNetServerSignalSetup): Initialize fds.

src/rpc/virnetserver.c

@@ -471,7 +471,7 @@ cleanup:
 
 static int virNetServerSignalSetup(virNetServerPtr srv)
 {
-    int fds[2];
+    int fds[2] = { -1, -1 };
 
     if (srv->sigwrite != -1)
         return 0;