nother attempt to add more logging and fix wallace messages not being delivered and staying in spool directory

Summary: Adding more logs that should show why _sendmail function does not start a "while" delivery loop and unliking file does not happen. Also some code polishing.

Test Plan: none

Reviewers: machniak, vanmeeuwen

Reviewed By: machniak

Subscribers: petersen

Differential Revision: https://git.kolab.org/D599