Two more memory leak fixes, on error paths I didn't spot in r9919.

[originally from svn r9948]
[r9919 == ea301bdd9b]

unix/uxproxy.c

@@ -288,6 +288,7 @@ Socket platform_new_connection(SockAddr addr, char *hostname,
     if (pipe(to_cmd_pipe) < 0 ||
 	pipe(from_cmd_pipe) < 0) {
 	ret->error = dupprintf("pipe: %s", strerror(errno));
+        sfree(cmd);
 	return (Socket)ret;
     }
     cloexec(to_cmd_pipe[1]);