Pause/unpause was being partially tested under the start/stop test.
This removes it from that test and adds dedicated pause + unpause
tests.
Note that the tests assert on current behavior, though it's been
noted where that is undesirable due to divergence from the Docker
CLI. Will change the behavior + update tests in a subsequent PR.
Signed-off-by: Milas Bowman <milas.bowman@docker.com>
Milas Bowman