Demote admin-passwd from core of API v3 as extensions os-admin-password

This patch move the action 'change_password' from core into extensions.
* Catch exception InstancePasswordSetFailed explicitly
* Add decorator 'expected_errors'
* Change naming style of action name and attributes
* Add testcase

Partially implements: bp v3-api-extension-versioning

DocImpact

Change-Id: I35fb73a47a58584ad6f8af78ffa087ecebde92a8
Merge "Demote admin-passwd from core of API v3 as extensions os-admin-password"