fixes #1595
cancels schedules tasks when needed
fixes #1595
fix removing tasks
executor service improvements
MapStore changed to use single thread executor
fixes #1595
fix removing tasks
fix removal of registered executor for mapstore
fix bug on MultiMap remove
Merge pull request #1614 from eminn/maintenance-3.x

[backport] MapStore changed to use single thread executor
Merge pull request #1671 from eminn/fix/MultiMapTxnRemove

fix bug on MultiMap remove
Merge pull request #1613 from enesakar/maintenance-i-1595

[backport] fixes #1595
Cleaned up ThreadDumpGenerator