[autotest] Add get_release_version method to servo_host

get_build_id method in autoupdater was removed. Add the new method for
servo_host to use.

BUG=chromium:472135
TEST=local servo test, confirm verify servo works

Change-Id: Ic255dce3b7bfa361204bd6dd7bb03b8f86ec6c5e
Reviewed-on: https://chromium-review.googlesource.com/263245
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
diff --git a/client/common_lib/cros/autoupdater.py b/client/common_lib/cros/autoupdater.py
index b39be92..5dd930b 100644
--- a/client/common_lib/cros/autoupdater.py
+++ b/client/common_lib/cros/autoupdater.py
@@ -590,7 +590,7 @@
                 # The crash names contain timestamps that may be useful:
                 #   kernel.20131207.005945.0.kcrash
                 for crash in kernel_crashes:
-                  logging.debug('  %s', os.path.basename(crash))
+                    logging.debug('  %s', os.path.basename(crash))
 
             # Print out some information to make it easier to debug
             # the rollback.