[autotest] Add dut-status --diagnosis.

This adds a new --diagnosis option to the dut-status command that
automatically displays all logs in a sequence leading to a DUT
failure.

This change also plumbs in a new RPC call needed to support the
feature.

BUG=chromium:492662
TEST=Run the command with the new option using a local RPC server

Change-Id: Ibb7431199bd0f8bbfe06fb8fffcb59512b01ab5b
Reviewed-on: https://chromium-review.googlesource.com/281205
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
diff --git a/server/frontend.py b/server/frontend.py
index bca99f8..6e8f817 100644
--- a/server/frontend.py
+++ b/server/frontend.py
@@ -325,10 +325,16 @@
 
     def get_host_status_task(self, host_id, end_time):
         task = self.run('get_host_status_task',
-                         host_id=host_id, end_time=end_time)
+                        host_id=host_id, end_time=end_time)
         return SpecialTask(self, task) if task else None
 
 
+    def get_host_diagnosis_interval(self, host_id, end_time, success):
+        return self.run('get_host_diagnosis_interval',
+                        host_id=host_id, end_time=end_time,
+                        success=success)
+
+
     def create_job_by_test(self, tests, kernel=None, use_container=False,
                            kernel_cmdline=None, **dargs):
         """