virtio-9p-proxy: fix error return in proxy_init()

proxy_init() does not check the return value of connect_namedsocket(),
fix this by rearranging code a little bit.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/9pfs/virtio-9p-proxy.c

@@ -1155,10 +1155,12 @@ static int proxy_init(FsContext *ctx)
         sock_id = atoi(ctx->fs_root);
         if (sock_id < 0) {
             fprintf(stderr, "socket descriptor not initialized\n");
+        }
+    }
+    if (sock_id < 0) {
         g_free(proxy);
         return -1;
     }
-    }
     g_free(ctx->fs_root);
     ctx->fs_root = NULL;