[autotest] Use the metrics_mock object in case chromite is not set up.

BUG=chromium:688166
TEST=unittest

Change-Id: Ic0077cb2dba75a8d820f229060f3f70f507850a1
Reviewed-on: https://chromium-review.googlesource.com/438754
Commit-Ready: Dan Shi <[email protected]>
Tested-by: Dan Shi <[email protected]>
Reviewed-by: Dan Shi <[email protected]>
diff --git a/server/site_crashcollect.py b/server/site_crashcollect.py
index 9601c08..892a8a0 100644
--- a/server/site_crashcollect.py
+++ b/server/site_crashcollect.py
@@ -14,7 +14,10 @@
 from autotest_lib.server.crashcollect import collect_log_file
 from autotest_lib.server import utils
 
-from chromite.lib import metrics
+try:
+    from chromite.lib import metrics
+except ImportError:
+    metrics = client_utils.metrics_mock
 
 
 def generate_minidump_stacktrace(minidump_path):