Fix bug to prevent continuous presence TTL timeouts.

Fix bug to prevent continuous presence TTL timeouts.

Change return value of static function's overflow condition to very
large value so that presence TTL timeout will not keep firing.

Change-Id: I63a79b692b13664ad62c95bec6657244df2ec9dd
Signed-off-by: Doug Hudson <douglas.hudson@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/831
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Mandeep Shetty <mandeep.shetty@intel.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>