Improve --debug logging output

This change makes the following improvements to the output of a
ceilometer command with the --debug option set:

* Silences spurious logging from iso8601 and urllib3.connectionpool
* Removes the line number from the logging format, since the intent
  of --debug is to show the user what network requests are occuring.

Change-Id: I1b286adf63b1ca05ec4fcfb27fbc939aa662cc7e
Closes-bug: #1324470
Merge "Improve --debug logging output"