Fix resolving destination queue name.

When subscription is closed releaseAckTrackingSinceChannelClosed is called which tried to resolve destination queue name in an invalid that leads to an exception.
Merge pull request #68 from sajinidesilva/slots_Imp

Slots imp - minor modifications
Merge pull request #66 from akalankapagoda/patch-1

Fix resolving destination queue name.
Slot impl - changed logs