Can not remove a part of deployed node roles

[Julia Aranovich]

Node roles assignment handler (https://github.com/openstack/fuel-web/blob/master/nailgun/nailgun/api/v1/handlers/assignment.py) does not support the following case:

1. deploy a node with a few roles (let it be controller + cinder)
2. then mark its cinder role as pending deletion
3. redeploy the node to leave controller role only on it

For now, there is a workaround: to remove this controller+inder node from an environment and add it back with controller role only. But this way requires 2 deployments.

Proposed solution: ?

[Julia Aranovich (jkirnosova)]

Also please consider the following cases:

1.1 How to set a node 'pending_deletion' flag from true to false using node assignment handler (user wants to revert removal a node from its environment)?

1.2 How to reset pending roles of a deployed node using node assignment handler (user wants to revert adding of new roles to a deployed node)? Now it's impossible because NodeUnassignmentHandler always sets 'pending_deletion' node flag to true.