Translate more REST API error messages

There were a few exception messages that were not being
translated because they were being wrapped and modified
before being turned into wsgi.Fault objects by
FaultWrapper. This adds some translation handling to
the FaultWrapper so we can get these messages localized
to the client's language specified in the Accept-Language
header.

Additionally adds a test to verfiy FaultWrapper is
translating any exception messages that can be.

fixes bug 1225226

Change-Id: I3847cff0ac4b37f57eb04b27150c4e0d1ea23f29
Merge "Translate more REST API error messages"