* https://review.openstack.org/#/c/526844/ move the intree
bundled tempest plugin to a new repo monasca-tempest-plugin.
Let's use it and remove the bundled tempest plugin from repo.
* Moved post_host script to main root directory
* Removed dummy gate_hook.sh script
* Fixed the jobs for the same
Story: 2001400
Task: 6085
Depends-On: I2ce2bd8238d44a451faeba9ddbfe27d900e9adef
Change-Id: I79cea368271bbef33914dba7b95f5546a1b8d3c1