Return correct stack result on malloc fail in ocstack.c

Return correct stack result on malloc fail in ocstack.c

Assign OC_STACK_NO_MEMORY to result variable when memory allocation
fails before jumping to exit.

Change-Id: I99c8f4ee18d82ef1b6a70c29b4625a06f61f7e4a
Signed-off-by: Mandeep Shetty <mandeep.shetty@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/460
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>
Reviewed-by: Sudarshan Prasad <sudarshan.prasad@intel.com>