Fix memory leak when CEL is successfully written to PostgreSQL database

Fix memory leak when CEL is successfully written to PostgreSQL database

PQClear is not called when the result object of a call to PQExec has a
status of PGRES_COMMAND_OK.  Interestingly enough, the off nominal case was
handled properly, so this memory leak only occurred when CEL records were
successfully written.

This patch properly clears the result in the nominal code path.

(closes issue ASTERISK-19991)
Reported by: Etienne Lessard
Tested by: Etienne Lessard
patches:
  mem_leak_cel_pgsql.patch uploaded by Etienne Lessard (license #6394)
........

Merged revisions 372158 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@372165 65c4cc65-6c06-0410-ace0-fbb531ad65f3