channels: Fix ssh_channel_from_local()

It only worked if the first channel in the list was equivalent to we
were looking for.
(cherry picked from commit 39f962c91e)

src/channels.c

@@ -300,24 +300,25 @@ static int channel_open(ssh_channel channel, const char *type_c, int window,
   return err;
 }
 
-/* get ssh channel from local session? */
+/* return channel with corresponding local id, or NULL if not found */
 ssh_channel ssh_channel_from_local(ssh_session session, uint32_t id) {
     ssh_channel initchan = session->channels;
-  ssh_channel channel;
+    ssh_channel channel = initchan;
 
-  /* We assume we are always the local */
+    for (;;) {
-  if (initchan == NULL) {
+        if (channel == NULL) {
             return NULL;
         }
-
+        if (channel->local_channel == id) {
-  for (channel = initchan; channel->local_channel != id;
+            return channel;
-      channel=channel->next) {
+        }
         if (channel->next == initchan) {
             return NULL;
         }
+        channel = channel->next;
     }
 
-  return channel;
+    return NULL;
 }
 
 /**