Adjust audit logs to avoid negative disk info

When requesting more disk than is available, the audit
logs will report negative values. This may confuse the
user or make him/her think the tracking is innaccurate.

This patch seeks to remove any confusion. It is in the
same vein as https://review.openstack.org/#/c/93261/
which addresses the same issue in regards to cpu and
memory audit logs.

Change-Id: I184985573b20144717ac40f1f3c26709030d5a03
Closes-bug: #1350542
Put a cap on our cyclomatic complexity

flake8 has support for cyclomatic complexity (Mccabe) currently our
worst offender has a complexity of 67 (25 is considered very bad). So
set our max-complexity to 68 so we at least don't make things any worse.

This is the first step in bringing this number down to 25 or so.

https://github.com/flintwork/mccabe

Change-Id: I5117ca58ad28888e24c16251aa5e92084ead97ca
Merge "XenAPI: Inform XAPI who is connecting to it"
Merge "Adjust audit logs to avoid negative disk info"
Merge "Put a cap on our cyclomatic complexity"