Revert "Changed sms2irc app to use Router.get_backend."
Revert "Changed sms2irc app to use Router.get_backend."

This reverts commit 93e7a5ab614a02b29733ebe0f90f74fdfd9d6652.

Uh, that didn't really work as expected.

rapidsms/rapidsms-legacy,rapidsms/rapidsms-legacy,rapidsms/rapidsms-legacy