[autotest] Rename build target from beaglebone to beaglebone_servo

Related CL:
https://chromium-review.googlesource.com/#/c/180682/

BUG=None
TEST=manual test against local devserver
CQ-DEPEND=CL:181875

Change-Id: Id909497ce30ac57e34ec4bf0187eb2abf9e7b4ac
Reviewed-on: https://chromium-review.googlesource.com/181814
Reviewed-by: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
diff --git a/global_config.ini b/global_config.ini
index 9be7345..3d44fec 100644
--- a/global_config.ini
+++ b/global_config.ini
@@ -169,7 +169,7 @@
 log_url_pattern: http://%s/tko/retrieve_logs.cgi?job=/results/%s/
 package_url_pattern: %s/static/%s/autotest/packages
 servo_url_pattern: %s/static/servo-images/%s_test_image.bin
-servo_builder: beaglebone-release
+servo_builder: beaglebone_servo-release
 
 # Username and password for connecting to remote power control switches of
 # the "Sentry Switched CDU" type