Get absolute value when resolving the slot Id.
Merge pull request #129 from akalankapagoda/GetAbsSlotId

Get absolute value when resolving the slot Id.
fix issue of ack receive not decrementing slot message count.
Merge pull request #130 from abeykoon/fix_message_delivery_after_trackerChange_02

fix issue of ack receive not decrementing slot message count.