Moved the methods into app/models/miq_server.rb and
app/models/miq_server/worker_management/quiesce.rb since each of those
files are basically the ones that use them.

`kill_all_workers` will actually be moved in a later commit to
modularize the core methods of MiqServer.

Moves them into a module for reusablity.  Freezes ones that haven't been
frozen already.

Moves common methods out of MiqServer to be reused in a later commit.

Moves "srsly everything" in app/models/miq_server/worker_management.rb
into it's own module for reuse.

Used a concern here since it seems to handle things better, but can't
use `include_concern` because that doesn't support non-standard paths
(yet...)

Allows MiqServerQueueManagement to be reused without loading MiqServer