Update the regex for finding the payload.

When this test is gonna run in the CQ the path to CQ build payloads are
different. So need to make the regex work for both by making it more
generic.

BUG=chromium:1113433
TEST=autoupdate_Basic.full

Change-Id: Id555bb6ae56dbcc46b9b4dedb97f9382b689bb81
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2500414
Tested-by: David Haddock <dhaddock@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Kyle Shimabukuro <kyleshima@chromium.org>
Commit-Queue: David Haddock <dhaddock@chromium.org>
diff --git a/server/cros/update_engine/update_engine_test.py b/server/cros/update_engine/update_engine_test.py
index 95984f9..a3186b2 100644
--- a/server/cros/update_engine/update_engine_test.py
+++ b/server/cros/update_engine/update_engine_test.py
@@ -289,8 +289,7 @@
         if is_dlc:
             payload_prefix = 'dlc_*%s*_%s_*' % (build.rpartition('/')[2], '%s')
         else:
-            payload_prefix = 'chromeos_%s*_%s_*' % (build.rpartition('/')[2],
-                                                    '%s')
+            payload_prefix = 'chromeos_*_%s_*.bin'
 
         regex = payload_prefix % ('full' if full_payload else 'delta')