[autotest] Add support of LATEST for android build.

With this change, android build can have LATEST as build id.

BUG=chromium:548881
TEST=local
http://dshi/afe/#tab_id=view_job&object_id=3017

Change-Id: I54b416548be5003f592e68fa6cb2d91034e14a5b
Reviewed-on: https://chromium-review.googlesource.com/315680
Commit-Ready: Dan Shi <dshi@google.com>
Tested-by: Dan Shi <dshi@google.com>
Reviewed-by: Fang Deng <fdeng@chromium.org>
diff --git a/global_config.ini b/global_config.ini
index 9df691b..aabd73f 100644
--- a/global_config.ini
+++ b/global_config.ini
@@ -250,7 +250,7 @@
 gs_offloader_use_rsync: False
 
 # Naming convention of Android build.
-android_build_name_pattern: %\(branch\)s/%\(target\)s/%\(build_id\)s'
+android_build_name_pattern: %\(branch\)s/%\(target\)s/%\(build_id\)s
 
 firmware_url_pattern: %s/static/%s/firmware_from_source.tar.bz2
 factory_image_url_pattern: %s/static/canary-channel/%s/factory_test/chromiumos_factory_image.bin