Demote "Logged transaction:" log messages from warning to info.

There are already error-level messages highlighting this state, and
marking these as "warnings" adds nothing to problem discoverability
(while obscuring other, probably more useful warnings).  They are
useful informational messages, but "info" logging is sufficient here.
Merge pull request #103 from apmichaud/master

Demote "Logged transaction:" log messages from warning to info.