This allows the user to specify a custom results directory root. cbuildbot can
be switched to use cros_run_parallel_vm_tests if necessary without any further
changes.
Also create parents directories for user-specified results directory roots in
run_remote_tests.
BUG=8585
TEST=./bin/cros_run_parallel_vm_tests suite_Smoke suite_Smoke \
--results_dir_root=/tmp/foo
Change-Id: I7314c1d9e74ca139eaa4bd95290866a43a3606ff
Review URL: http://codereview.chromium.org/4297003
Current usage is simple: just specify a list of tests and each one will be run
on a separate VM using the latest image on a default board. Exit code is
non-zero if any of the tests fail. Output from separate tests is interleaved.
More CLs to follow -- specifying a result directory, non-interleaved output,
base ssh port, board, image path, etc.
BUG=8585
TEST=./bin/cros_run_parallel_vm_tests suite_Smoke suite_Smoke
Change-Id: Ifa3396768050905ec02e4cad8b8f065a6d129154
Review URL: http://codereview.chromium.org/4337003
