Add hw test as an option for remote trybot

User can specify "--hwtest" to turn on hw testing for remote trybot. The
feature is off by default. This change passes 'trybot-target/version'
(e.g. 'trybot-lumpy-paladin/R22-2515.0.0-a1-b127') as an unique label to
the autotest server, as opposed to 'target/version' in the buildbot runs.
Hence the artifacts are stored at
GOOGLE_STORAGE_URL_PREFIX/chrome-image-archive/trybot-target/version/

BUG=chromium-os:32272
TEST=unittest & remote trybot run using --bootstrap-args

Change-Id: I07554de1c36e55bac0168b69640082d746bced23
Reviewed-on: https://gerrit.chromium.org/gerrit/26074
Tested-by: Yu-Ju Hong <yjhong@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Ready: Yu-Ju Hong <yjhong@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index dfceecd..6e1fd03 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -805,6 +805,9 @@
   group.add_remote_option('--clobber', action='store_true', dest='clobber',
                           default=False,
                           help='Clears an old checkout before syncing')
+  group.add_remote_option('--hwtest', dest='hwtest', action='store_true',
+                           default=False,
+                           help='This adds HW test for remote trybot')
   group.add_remote_option('--lkgm', action='store_true', dest='lkgm',
                           default=False,
                           help='Sync to last known good manifest blessed by '