lurch_devman: utilize async start/stop
lurch_devman: split test setup functions

Some tests needs only mocked lurch_dev, other need also lurch_devman
gen_server. Split the setup functions so only necessary requisities are
started for them.
lurch_devman: test stop response
lurch_devman: add fault insertion tests

Try to handle async events with invalid tag.
It's probably an overkill - where should those messages come from
anyway?
lurch_devman: more descriptive variable name
lurch_dev: do not stop the port when terminated normally

The port is already stopped due to stop call.
lurch_dev: remove the 'sync' procedures

They won't be used anyway.
lurch_dev: enable server scenario test