chan_pjsip: AMI action PJSIPShowEndpoint closes AMI connection on error.

Also fixed similar problem with AMI action PJSIPShowEndpoints.

ASTERISK-24872 #close
Reported by: Dmitriy Serov

Review: https://reviewboard.asterisk.org/r/4487/
........

Merged revisions 432894 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@432895 65c4cc65-6c06-0410-ace0-fbb531ad65f3