pbx_app: Update outdated pbx_exec channel snapshots.

pbx_exec makes a channel snapshot before executing applications.
This doesn't cause an issue during normal dialplan execution
where pbx_exec is called over and over again in succession.
However, if pbx_exec is called "one off", e.g. using
ast_pbx_exec_application, then a channel snapshot never ends
up getting made after the executed application returns, and
inaccurate snapshot information will linger for a while, causing
"core show channels", etc. to show erroneous info.

This is fixed by manually making a channel snapshot at the end
of ast_pbx_exec_application, since we anticipate that pbx_exec
might not get called again immediately.

ASTERISK-30367 #close

Change-Id: I2a5131053aa9d11badbc0ef2ef40b1f83d0af086

main/pbx_app.c

@@ -519,6 +519,8 @@ int ast_pbx_exec_application(struct ast_channel *chan, const char *app_name, con
 			}
 			res = pbx_exec(chan, app, app_args);
 		}
+		/* Manually make a snapshot now, since pbx_exec won't necessarily get called again immediately. */
+		ast_channel_publish_snapshot(chan);
 	}
 	return res;
 }