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 <[email protected]> Reviewed-by: Jason Glasgow <[email protected]> Tested-by: Jason Glasgow <[email protected]>