fence-virt: Fix free of uninitialized variable

Fix a possible free() of an uninitialized struct member in
the error path that's hit in an OOM situation.

Signed-off-by: Ryan McCabe <rmccabe@redhat.com>

server/virt-sockets.c

@@ -108,7 +108,7 @@ domain_sock_setup(const char *domain, const char *socket_path)
 	free(sun);
 	sun = NULL;
 
-	node = malloc(sizeof(*node));
+	node = calloc(1, sizeof(*node));
 	if (!node)
 		goto out_fail;