Do not try to introspect nodes in maintenance mode and associated ones
Do not try to introspect nodes in maintenance mode and associated ones

Some time ago ironic-discoverd used to require maintenance mode.
This was changed back in Kilo, and was deprecated in Liberty.

Also cleans up introspection code a bit.

Change-Id: Ib2ea84a8e7f0a42423199cd1db40136ab8495fdc

openstack/python-tripleoclient