Rework extension verification in verify_tempest_config

Due to several changes being made to the config nomenclature around
features and extensions in tempest the verify_tempest_config script
was actually not valid anymore. This commit fixes the script to use
the updated config structure. Additionally it adds support for all
3 api's in tempest that currently have extensions api clients:
nova, nova_v3, and cinder.

Partially implements bp config-verification

Change-Id: I35c325c5f57803b36906bde13f132b69509f5e85
Remove vim headers 2nd round

We don't need to have the vim headers in each source files. So we have
already removed all of it at
 Change-Id: I43703e2289212389c7841f44691ae7849ed1f505
However, some files still have it now because of the patch time lag.
Maybe, we should have a hacking rule for this. But it's out of scope
here.

Change-Id: I8d09cb41ad633719857973a3ea228cd8dd3a9270
Closes-Bug: #1229324
Merge "Remove vim headers 2nd round"
Merge "Rework extension verification in verify_tempest_config"