Logging audit for trove/guestagent module

Adjust logging to conform to logging standards. Found
and fixed a pattern of not logging exception information.
Cleaned up some messages that were unclear.

Also addressed a pattern of having exception's using
LOG.error to log the exception (rather than using
LOG.exception).

Change-Id: Idab510051321f4f9ed096c9972322530028ad2e6
Partial-Bug: #1324206
Merge "Logging audit for trove/guestagent module"