Make provision_devices failures abort the build

Otherwise if the devices are gone lots of tests will just fail.

Already fixed this for recipe based builders in crbug.com/393681

I don't know how to test this, but happy to write one if shown.

BUG=393681
NOTRY=True

Review URL: https://codereview.chromium.org/390993003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283890 0039d316-1c4b-4281-b951-d872f2087c98

build/android/buildbot/bb_device_steps.py

@@ -414,7 +414,7 @@ def ProvisionDevices(options):
     provision_cmd.append('--auto-reconnect')
   if options.skip_wipe:
     provision_cmd.append('--skip-wipe')
-  RunCmd(provision_cmd)
+  RunCmd(provision_cmd, halt_on_failure=True)
 
 
 def DeviceStatusCheck(options):