943 release openhelpermanager

Implement #943 issue.

Please review my code. Thx!
If the test is running, CI will first execute the `OrmLiteActivityTest` which is set the `instanceCount` to 8(getHelper was invoked repeatedly). 

When we arrived at the `OrmLiteOnDestroyTest`, the process was not restarted, then this field of the value was still 8. Test failed.

I have annother solution:
Add the `tearDown` in these classes, only reset all of the `OpenHelperManager`'s fields.
Thus each test-case is clean, ease to run. :)