Plug a memory leak in res_config_ldap.

(closes issue #16257)
Reported by: nito
Patches:
      issue16257_20100111.diff uploaded by seanbright (license 71)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@240271 65c4cc65-6c06-0410-ace0-fbb531ad65f3