flimflam: flimflam.py: allow SetDebugTags to function with shill

Handle failures to SetDebugTags gracefully by trying to set the debug
level which is all that can be done with shill.

BUG=chromium-os:25566
TEST=run network_3GModemControl

Change-Id: I699e49923f93eb7a3d41012d9c2104e3e4581bb8
Reviewed-on: https://gerrit.chromium.org/gerrit/14937
Commit-Ready: Jason Glasgow <jglasgow@chromium.org>
Reviewed-by: Jason Glasgow <jglasgow@chromium.org>
Tested-by: Jason Glasgow <jglasgow@chromium.org>

test/flimflam.py

diff --git a/test/flimflam.py b/test/flimflam.py
index bc11d6d..652c8ea 100644
--- a/test/flimflam.py
+++ b/test/flimflam.py
@@ -329,7 +329,17 @@
         return self.manager.ListDebugTags()
 
     def SetDebugTags(self, taglist):
-        self.manager.SetDebugTags(taglist)
+        try:
+            self.manager.SetDebugTags(taglist)
+        except dbus.exceptions.DBusException, error:
+            if error.get_dbus_name() not in [
+              "org.freedesktop.DBus.Error.UnknownMethod" ]:
+                raise error
+            # Shill implements SetDebugLevel not SetDebugTags
+            self.SetDebugLevel(4)
+
+    def SetDebugLevel(self, level):
+            self.manager.SetDebugLevel(level)
 
     def ConvertSSID(self, ssid_list):
         ssid = ""