[autotest] Add a 'repair_hosts' command.

We have a `reverify_hosts` command for triggering Verify tasks, but
nothing for triggering Repair tasks.  So, add the command.

BUG=chromium:754362
TEST=Run against a couple of working, idle DUTs in the lab

Change-Id: I9901d9aa5fb3852bd93013e768681e5e259b15c3
Reviewed-on: https://chromium-review.googlesource.com/611252
Commit-Ready: Richard Barnette <jrbarnette@chromium.org>
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
diff --git a/server/frontend.py b/server/frontend.py
index 452d3bf..a643ff4 100644
--- a/server/frontend.py
+++ b/server/frontend.py
@@ -545,6 +545,15 @@
         return self.run('reverify_hosts', **query_args)
 
 
+    def repair_hosts(self, hostnames=(), status=None, label=None):
+        query_args = dict(locked=False,
+                          aclgroup__users__login=self.user)
+        query_args.update(self._dict_for_host_query(hostnames=hostnames,
+                                                    status=status,
+                                                    label=label))
+        return self.run('repair_hosts', **query_args)
+
+
     def create_host(self, hostname, **dargs):
         id = self.run('add_host', hostname=hostname, **dargs)
         return self.get_hosts(id=id)[0]