Nested jails #25

Testing with nested Jails has brought up some bugs:

• At the moment, BuildBot builds are failing because we seem to be handling nested jails things rather flakily - namely we're setting properties that we aren't allowed to in the tests.

  • We should conditionally disable these in the tests.

• RCTL doesn't work in Jails (Don't fail tests when RCTL is not enabled #22):

  • as of version 0.0.3 of rctl, (rctl: Fail graciously in a jail #23), the status check reports an invalid kernel state when attempting to use RCTL inside a jail.
  • this broke jail teardown (rctl: Don't inhibit teardown if rctl not enabled #24)