Cluster 'components' field does not contain values declared by an enabled plugin

[Igor Zinovik]

Plugin contains .py script that adds restrictions to roles that are not applicable
to environment with the plugin.

Steps to reproduce:
1. Create new environment with NSXv plugin
2. Open "Add nodes" pane.

Expected result:
Compute, Cinder and Ironic roles are not shown.

Actual result:
Compute, Cinder and Ironic roles are show. It is possible to assign them
to nodes, but actually it is not possible to use them.

Bug found on Fuel NSXv plugin commit f326348f530b80ee012584dd759d577c8e94b131

Script works fine if executed directly by user. Seems that post_install action
uses wrong path to script.

[Igor Zinovik (izinovik)]

Fix commited https://review.openstack.org/#/c/335532

[Igor Zinovik (izinovik)]

Regression found in #771 build which includes patch for aforementioned problem.

[Igor Zinovik (izinovik)]

Seems that problem might be related to plugin components registration during
cluster creation.

Here is a 'clusters' table that contains 'components' field:
http://paste.openstack.org/show/526961/

First cluster was created by automated test - 'components' field is empty.
Two other clusters was created via fuel web UI and contain 'components' that
are declared by the plugin.

[Andriy Popovych (popovych-andrey)]

https://github.com/openstack/fuel-qa/blob/master/fuelweb_test/models/fuel_web_client.py#L484 should be extended to provide components via API.