[autotest] Make run_suite reimaging job reporting backward-compatible

run_suite should tolerate suite jobs that contain just the one line for reimaging
jobs, as opposed to per-host reports.

BUG=chromium-os:22060
TEST=run_suite.py -m <old suite job id>

Change-Id: Ifabc6e98ccf96717a031be7f6c836d7a0b3c2f9d
Reviewed-on: https://gerrit.chromium.org/gerrit/26347
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Ready: Chris Masone <cmasone@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
diff --git a/site_utils/run_suite.py b/site_utils/run_suite.py
index e5144f5..c5fc195 100755
--- a/site_utils/run_suite.py
+++ b/site_utils/run_suite.py
@@ -157,7 +157,10 @@
         if entry['test_name'] == 'SERVER_JOB':
             self.suite_start_time = start_candidate
         elif entry['test_name'].startswith('try_new_image'):
-            hostname = entry['test_name'].split('-', 1)[1]
+            if '-' in entry['test_name']:
+                hostname = entry['test_name'].split('-', 1)[1]
+            else:
+                hostname = ''
             self.reimage_times[hostname] = (start_candidate, end_candidate)
         else:
             self._UpdateFirstTestStartTime(start_candidate)