TAP test for recovery_end_command

Hi,

The attached patch adds a small test for recovery_end_command execution.

Currently, patch tests execution of recovery_end_command by creating
dummy file, I am not wedded only to this approach, other suggestions
also welcome.

Also, we don't have a good test for archive_cleanup_command as well, I
am not sure how we could test that which executes with every
restart-point.

Thanks to my colleague Neha Sharma for confirming the test execution on Windows.

Regards,
Amul