Refactoring to remove GDAPI as constructor argument to ResponseUnpacker
Fixes an issue where a slave would endlessly try to catch up with master

when starting up in HA. The problem was that the target txId was
constantly moving with every commit made on the master.

This commit reads the target txId ones and stops streaming when arriving
there.
Merge pull request #3203 from tinwelint/2.2-fix-endless-catchup

[2.2] Fixes an issue where a slave would endlessly try to catch up with master