AURORA-145:Test dependencies leak into distribution

Moves testing dependencies out of main src into test.

Testing Done:
Was initially waiting on AURORA-132 for this. ran build-support/jenkins/build.sh and created dists with no issues.

Bugs closed: AURORA-145

Reviewed at https://reviews.apache.org/r/19796/
Make testing of v1 command hooks easier.

In order to be able to test v1 command hooks on real commands, it would
be helpful to be able to mock out the body of the commands. In order to
do this, I've separated the commands into an invocation frame, and
the actual command implementation.

Bugs closed: aurora-603

Reviewed at https://reviews.apache.org/r/23949/