Fixed presence payload parsing logic (IOT-406)

Fixed presence payload parsing logic (IOT-406)

Updated method parsePresencePayload to handle scenarios
when payload is not in the expected presence format.
Also added unit test to verify parsing functionality.

Change-Id: I47d995b8f49cc96805bf837ac2c2f77c1859da82
Signed-off-by: Sachin Agrawal <sachin.agrawal@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/538
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>
Reviewed-by: Sashi Penta <sashi.kumar.penta@intel.com>