Remove misc.as_bool as oslo provides an equivalent

There isn't a need to have a misc.as_bool function
anymore now that we have imported the oslo incubator
strutils module since that module provides a function
that does *nearly* the same thing.

Change-Id: I7afe141d5a37c50b0c926144743f9af71db95bbf
Merge "Remove misc.as_bool as oslo provides an equivalent"