[autotest] Expand DevServer class to support control-file related calls

Add the ability to call the control_files/ endpoint on the dev server.

BUG=chromium-os:24985
TEST=dev_server_unittest.py

Change-Id: If20e7c6d1f13813cd10511c34d64e9ffddfb37f4
Reviewed-on: https://gerrit.chromium.org/gerrit/14302
Commit-Ready: Chris Masone <cmasone@chromium.org>
Reviewed-by: Chris Masone <cmasone@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
diff --git a/server/cros/dynamic_suite_unittest.py b/server/cros/dynamic_suite_unittest.py
index 696ce31..b96ab92 100755
--- a/server/cros/dynamic_suite_unittest.py
+++ b/server/cros/dynamic_suite_unittest.py
@@ -71,8 +71,8 @@
             return reduce(lambda b,i: "%s='%s'\n" % i in s, d.iteritems(), True)
 
         v = {'v1': 'one', 'v2': 'two'}
-        self.assertTrue(find_all_in(v, self.reimager._inject_vars(v, '')))
-        self.assertTrue(find_all_in(v, self.reimager._inject_vars(v, 'ctrl')))
+        self.assertTrue(find_all_in(v, dynamic_suite.inject_vars(v, '')))
+        self.assertTrue(find_all_in(v, dynamic_suite.inject_vars(v, 'ctrl')))
 
 
     def testReportResultsGood(self):