INT-2825 Remove Temporary 2.2. Interface

AbstractTransactionSynchronizingPollingEndpoint was introduced late in the 2.2 release process to avoid a breaking change to AbstractPollingEndpoint. For 3.0, its methods are now pulled-up into APE.

Further change:

* remove Deprecated Setter (PollerMetadata)
* fix failing test
Merge pull request #717 from garyrussell/INT-2825

* garyrussell-INT-2825:
  INT-2825 Remove Temporary 2.2. Interface