Adding OCException unit tests

Adding OCException unit tests

Adding a bunch of unit tests to validate the functionality of
OCException.

Also removed the unused 'reason' function that didn't use 'this'

Change-Id: I34bac1c06b2bc755a0af19e3ddcc1ac9ae3611fc
Signed-off-by: Erich Keane <erich.keane@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/584
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Sakthivel Samidurai <sakthivel.samidurai@intel.com>
Reviewed-by: Sudarshan Prasad <sudarshan.prasad@intel.com>