Do not append to messages with +

Some code was appending to translated messages using +, which
oslo-incubator's new gettextutils doesn't support.

The code was changed to use a substitution value in the message
instead.

Part of bp user-locale-api

Change-Id: If2bc1821d0057c4cd53ead7eac1712284464b9bf
Merge "Do not append to messages with +"