Fix segfault on presence payload destroy.

Fix segfault on presence payload destroy.

Two pointers pointd to the same memory location and both pointers were
free'd. One was free'd explicitly and the other was free'd as part of
freeing a struct in OCPresencePayloadDestroy.

Change-Id: Ieb3517ffeb4ab0abc4e6e7ff2b6b3b44a82264bf
Signed-off-by: Mandeep Shetty <mandeep.shetty@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2086
Reviewed-by: Omkar Hegde <omkar.m.hegde@intel.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>