This isn't a real subcommand like the others. The option processing
just intercepts it and prints the output. Given that we're subcommand
based, it makes sense to support this in addition to --help.
The API server will run a mock compose when a test mode is passed to it.
Passing a 1 will queue a build, pretend to run the build for 10 seconds,
and then fail. Passing a 2 will do the same thing, but it will finish as
if it was successful. All results are available but the output file is
only the string "TEST IMAGE"
This should allow running tests inside docker without calling anaconda
(becuase it will not run in docker, it needs a VM).
