Adds Environment File for Removing Sahara during M/N upgrade

Adds Environment File for Removing Sahara during M/N upgrade

The default path if the operator does nothing is to keep the
sahara services on mitaka to newton upgrades.

If the operator wishes to remove sahara services then they
need to specify the provided major-upgrade-remove-sahara.yaml
environment file in the stack upgrade commands.

The existing migration to ha arch already removes the constraints
and pcs resource for sahara api/engine so we just need to stop
it from starting again if we want to remove it.

This adds a  KeepSaharaServiceOnUpgrade parameter to determine if
Sahara is disabled from starting up after the controllers are
upgraded (defaults true).

Finally it is worth noting that we default the sahara services
as 'on' during converge here in the resource_registry of the
converge environment file; any subsequent stack updates where
the deployment contains sahara services will need to
include the -e /environments/services/sahara.yaml environment
file.

Related-Bug: 1630247
Change-Id: I59536cae3260e3df52589289b4f63e9ea0129407