patch 8.0.1083: leaking memory in input part of channel

Problem:    Leaking memory in input part of channel.
Solution:   Clear the input part of channel.  Free the entry. Move failing
            command test to a separate file to avoid bogus leak reports
            clouding tests that should not leak.
diff --git a/src/channel.c b/src/channel.c
index 0e9a580..fa1898d 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -2939,6 +2939,7 @@
 	wq->wq_prev = NULL;
     else
 	wq->wq_next->wq_prev = NULL;
+    vim_free(entry);
 }
 
 /*
@@ -2990,7 +2991,7 @@
     channel_clear_one(channel, PART_SOCK);
     channel_clear_one(channel, PART_OUT);
     channel_clear_one(channel, PART_ERR);
-    /* there is no callback or queue for PART_IN */
+    channel_clear_one(channel, PART_IN);
     free_callback(channel->ch_callback, channel->ch_partial);
     channel->ch_callback = NULL;
     channel->ch_partial = NULL;