Code review comment for lp:~tim-simpson/nova/multiple-notifiers

I pushed up a new version which instead of forcing the notifier.api to keep a list of drivers has a driver called "list_notifier" that can call a list of other drivers.

I thought calling it "fan_out_notifier" might infer additional qualities it lacked, so I went with a simpler name. I can rename it if anyone thinks the term "fan out" is a better fit.

Sandy this code has a test case for when one driver fails (it asserts an exception is logged) and another for when they all work.