Don't fail when unknown args are passed down to cros VM tast tests.

This is to prevent failures like https://ci.chromium.org/p/chromium/builders/luci.chromium.try/chromeos-amd64-generic-rel/141038

I'm tired of playing catch-up with all the additional gtest args we
keep adding to test retries.

Change-Id: I86e1180b62a8f47264c47c0bcb8c2d24a589928d
Reviewed-on: https://chromium-review.googlesource.com/c/1353996Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612365}

build/chromeos/run_vm_test.py

@@ -169,9 +169,9 @@ class TastTest(RemoteTest):
               '--gtest_repeat')]
 
     if self._additional_args:
-      raise TestFormatError(
-          'Tast tests should not have additional args: %s' % (
-              self._additional_args))
+      logging.error(
+          'Tast tests should not have additional args. These will be '
+          'ignored: %s', self._additional_args)
 
     self._vm_test_cmd += [
         '--deploy',