Fix status code for coverage API v3

* Change the status code of action 'reset' and 'stop' code to 204, and use
'wsgi.action' instead of action method.
* When stop coverage without started coverage will raise HTTPConflict
* Add decorator 'extensions.expected_errors'

Partially implements bp v3-api-extension-versioning

DocImpact

Change-Id: If9f873d85dbb10d9bfd1ae8a7122c3e3d94fc955
Port flavor_rxtx extension to v3 API Part 1

This changeset only copies the v2 files (implementation and test)
into the appropriate v3 directories unchanged. The copy as-is
will not be loaded by either the v2 or v3 extension loaders. The
second changeset will then make the changes required for it to
work as a v3 extension.

This is being done in order to make reviewing of extension porting
easier as gerrit will display only what is actually changed for v3
rather than entirely new files

Partially implements blueprint nova-v3-api

Change-Id: I560aacfcde07481c2bcc6d8ab4c785ba6e2c2e2b
Port flavor_rxtx extension to v3 API Part 2

Ports the flavor_rxtx extension and the corresponding
unittests to the v3 framework.

Partially implements blueprint nova-v3-api

Change-Id: Id486e157e4f5ce467400c88ca89952d175f6e9a8
Porting server metadata core api to API v3 Part 1

This changeset only copies the v2 files (implementation and test)
into the appropriate v3 directories unchanged. The copy as-is
will not be loaded by either the v2 or v3 extension loaders. The
second changeset will then make the changes required for it to
work as a v3 extension.

This is being done in order to make reviewing of extension porting
easier as gerrit will display only what is actually changed for v3
rather than entirely new files

Partially implements blueprint nova-v3-api

Change-Id: I705336c4bfb66e576e520e8b4293adf45ad63aa8
Porting server metadata core API to API v3 Part 2

This adapts server metadata API to v3 tree using the new extension
framework.
Partially implements bp v3-api-core-as-extensions

Change-Id: I2013ef255e00e256899f8048c97c1d6c73b3268f
Porting os-aggregates extensions to API v3 Part 1

This changeset only copies the v2 files (implementation and test)
into the appropriate v3 directories unchanged. The copy as-is
will not be loaded by either the v2 or v3 extension loaders. The
second changeset will then make the changes required for it to
work as a v3 extension.

This is being done in order to make reviewing of extension porting
easier as gerrit will display only what is actually changed for v3
rather than entirely new files

Partially implements blueprint nova-v3-api

Change-Id: Idb1fa71371d9a759b5ff2dd70e703aeece84cf5e
Porting os-aggregates extensions to API v3 Part 2

This includes a set of fixes and improvements to os-aggregates:
    - eliminate the action method replacing its functionality with wsgi.action
      decorator.
    - Returns explicity and appropriate status codes for each REST action.
    - Improves information error passed to the user.

In the unit test removes one test that in fact was testing the action method
itself instead of _remove_host and which no longer makes sense since action is
removed.

Partially implements blueprint nova-v3-api

Change-Id: Ie737333c6b058f5b57b3e7c75b3d3eda95b80402
Merge "Porting server metadata core api to API v3 Part 1"
Merge "Porting server metadata core API to API v3 Part 2"
Merge "Porting os-aggregates extensions to API v3 Part 1"
Merge "Porting os-aggregates extensions to API v3 Part 2"
Merge "Port flavor_rxtx extension to v3 API Part 1"
Merge "Port flavor_rxtx extension to v3 API Part 2"
Merge "Fix status code for coverage API v3"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp