As discussed at the summit in the QA stream, this removes
the coverage extension from the V2 API.
According to the API Change Guidelines
https://wiki.openstack.org/wiki/APIChangeGuidelines
we should not be doing this. However the coverage
extension is a rather special case. It has security issues
such that it shouldn't be used in a production cloud
environment. It also doesn't work properly so its usefulness
to measure API coverage is limited. And in the past the presence of
this plugin has been used as a reason not to accept
an alternative technique to measure API coverage.
This is the proposed replacement
https://review.openstack.org/#/c/25882/
Change-Id: I07d798129ee277a6f7691c25f88c07a5204c0943