Comment 4 for bug 1738614

It might be good to note that a machine level mutex is probably not a solution here
and for a pair of reasons:

1) Almost the entire operation would need to be locked by the Mutex as it is currently implemented

2) While this would work with a machine level mutex solution:

parallel 'juju add-model m{1}{2} --no-switch --debug; time wait' ::: `seq 0 9` ::: `seq 0 9`

the following would not:

parallel -Smachine1, machine2 'juju add-model m{1}{2} --no-switch --debug; time wait' ::: `seq 0 9` ::: `seq 0 9`