Fix lua goto detection to prevent unexpected behavior with confbridge

A bug in the pbx_lua goto detection was causing the dialplan to hangup
unexpectedly after confbridge exited if it had called lua dialplan code during
execution.

Patch-by: Timo Teras
Acked-by: Matt Nicholson
(closes issue ASTERISK-18976)
........

Merged revisions 349928 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@349929 65c4cc65-6c06-0410-ace0-fbb531ad65f3