Don't destroy confbridge config when error is encountered during a reload.

Not panicking means that the old config is kept.

(closes issue ASTERISK-20458)
Reported by: Leif Madsen
Patches:
	ASTERISK-20458.patch uploaded by Mark Michelson(license #5049)
Tested by Leif Madsen
........

Merged revisions 374106 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@374107 65c4cc65-6c06-0410-ace0-fbb531ad65f3