Clean up logging levels

The following logging levels are set according to the combination of
--verbose, --quiet and --debug options:

verbose_level   logging level       options
0               --quiet             ERROR
1               (none)              WARNING
2               --verbose           INFO
3+              --verbose --verbose DEBUG
                or --debug

Logging levels for the requests and iso8601 modules are forced to ERROR.

This is the first step in bp use-logging-not-print

The difference between '--debug' and '--verbose --verbose' is --debug triggers
cliff's exception handling and traceback display.

Change-Id: Ide2233b3316471d279260fb1e7255a6ca2072023
Merge "Clean up logging levels"