Rely on Portage to run required stages before "test" stage.

Previously, the cros unit test function was telling Portage exactly which
flow stages to run leading up to the "test" stage by giving the "noauto"
FEATURE and specifying each stage explicitly.  This proved unnecessarily
brittle, so now we rely on Portage's default behavior to determine which
stages must be run before the requested "test" stage.  Also added explicit
"clean" stage after test to remove all temporary files from disk.

Change-Id: I7e0a9e0ecc29eee2b564e78f9078a8da43b96167

TEST=./cros_run_unit_tests --board=x86-mario --packages=chromeos-wm

Review URL:
1 file changed