Automated tests for work with RHEL-based computes

Scope:
 * [Fuel-qa] Implement in fuel-qa mechanism of addition pre-provisioned node to cluster
 * [Fuel-qa] Review fuel-qa and select test suites which may check impact from
   RHEL-based computes. Add boolean option "RHEL-based compute nodes" in this tests.
   If value is True, then all compute nodes will be added to cluster as pre-provisioned nodes.
 * [Fuel-devops] Implement mechanism of preparation pre-provisioned node
 * [CI] Prepare snapshots wtih installed ang configured RHEL
 * [CI] Create Jenkins jobs

Additional scenarios to automate:

Label: "Install command"

1. Install plugin "support of RHEL-based compute"
2. Create cluster
3. Setup default plugins settings, exclude section "Install command"
4. Set certain value for field "Install command"
5. Add one node with role "controller"
6. Revert snapshot "ready_rhel_node"
7. Add pre-provisioned RHEL node with role "compute"
8. Run network check
9. Deploy changes
10. Run OSTF
11. Check that certain package

Label: "Additional repos"

1. Install plugin "support of RHEL-based compute"
2. Create cluster
3. Setup default plugins settings, exclude section "Repos"
4. Set new repo URL
5. Add one node with role "controller"
6. Revert snapshot "ready_rhel_node"
7. Add pre-provisioned RHEL node with role "compute"
8. Run network check
9. Deploy changes
10. Run OSTF

Label: "Unavailable repos"

1. Install plugin "support of RHEL-based compute"
2. Create cluster
3. Setup default plugins settings, exclude section "Repos"
4. Set new unavailable repo URL
5. Add one node with role "controller"
6. Revert snapshot "ready_rhel_node"
7. Add pre-provisioned RHEL node with role "compute"
8. Check Nailgun response code

Label: "Wrong install command"

1. Install plugin "support of RHEL-based compute"
2. Create cluster
3. Setup default plugins settings, exclude section "Install command"
4. Set certain value for field "Install command"
5. Add one node with role "controller"
6. Revert snapshot "ready_rhel_node"
7. Add pre-provisioned RHEL node with role "compute"
8. Check Nailgun response code

Label: ''Remove/disable plugins after addition pre-provisioned node"

1. Install plugin "support of RHEL-based compute"
2. Create cluster
3. Setup default plugins settings
4. Set certain value for field "Install command"
5. Add one node with role "controller"
6. Revert snapshot "ready_rhel_node"
7. Add pre-provisioned RHEL node with role "compute"
8. Try to remove/disable plugin
9. Check Nailgun response code

Label: "Hyprid cluster"

Delivery:
 * Automated tests in fuel-qa