[test] Fix test-listing command on Android

The cctest and unittests suites call the test executable to list the
tests, which requires pushing the executables to the device on Android.

NOTRY=true
TBR=sergiyb@chromium.org

Bug: chromium:866862
Change-Id: I318dff7af2b2de3b8642ec4b6ba30b602da808bb
Reviewed-on: https://chromium-review.googlesource.com/1213202Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55723}

tools/testrunner/local/command.py

@@ -211,7 +211,7 @@ class AndroidCommand(BaseCommand):
     """
     self.shell_name = os.path.basename(shell)
     self.shell_dir = os.path.dirname(shell)
-    self.files_to_push = resources_func()
+    self.files_to_push = (resources_func or (lambda: []))()
 
     # Make all paths in arguments relative and also prepare files from arguments
     # for pushing to the device.