Add enable/disable API functions to service manager
Add enable/disable API functions to service manager

Disable OpenStack APIs is a part of maintenance mode for the environment. Use
'disable' keyword to apply maintenance config to harpoxy.

`manage_services.sh disable ENV_ID`

Use 'enable' keyword to cancel maintenance mode of haproxy operation.

`manage_services.sh enable ENV_ID`

Specify ENV ID instead of explicit hosts file.

Mirantis/octane,stackforge/fuel-octane,Mirantis/octane,stackforge/fuel-octane