res_hep: Release allocation reference to configuration.

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


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@424312 f38db490-d61c-443f-a65b-d21fe96a405b