CI: increase unit test timeout
CI: increase unit test timeout

It appears that switching to the new ARD concourse has slowed down runs
of these unit tests by over 130% (~8 mins -> ~19 mins)

For now, I'm just going to increase the timeout. We should try and speed
this up though. Either by powering up the containers that tasks run in,
or by making these unit tests parallelizable.

cloudfoundry/cf-deployment,cloudfoundry/cf-deployment