res_hep: Release allocation reference to configuration.

ASTERISK-24362 #close
Reported by: Corey Farrell
Review: https://reviewboard.asterisk.org/r/4026/
........

Merged revisions 424312 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@424313 f38db490-d61c-443f-a65b-d21fe96a405b