fixes #1675 undefined behavior in posix ipc_dialer_dial

(This also affects TCP, and fixed there.)

src/platform/posix/posix_ipcdial.c

@@ -188,6 +188,8 @@ ipc_dialer_dial(void *arg, nni_aio *aio)
 	// This arranges for the fd to be in non-blocking mode, and adds the
 	// poll fd to the list.
 	if ((rv = nni_posix_pfd_init(&pfd, fd)) != 0) {
+		// the error label unlocks this
+		nni_mtx_lock(&d->mtx);
 		goto error;
 	}
 

src/platform/posix/posix_tcpdial.c

@@ -207,6 +207,8 @@ nni_tcp_dial(nni_tcp_dialer *d, const nni_sockaddr *sa, nni_aio *aio)
 	// poll fd to the list.
 	if ((rv = nni_posix_pfd_init(&pfd, fd)) != 0) {
 		(void) close(fd);
+		// the error label unlocks this
+		nni_mtx_lock(&d->mtx);
 		goto error;
 	}