Lockable resources plugin should not lock a resource when it is offline.
lock(label: <label>, quantity: 3, variable: 'RESOURCES')
will lock 3 resources without checking whether the nodes are offline
when the servers are taken out for maintenance or requires troubleshooting, currently there is no way to prevent lock on the offline resource without ADMIN access (which is basically removing the resource from the Lockable Resources Manager ).
Normal users (without ADMIN access) cannot control locks over an offline resource for maintenance/troubleshooting