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
Sync gettextutils from oslo-incubator 997ab277

Keystone's gettextutils package was behind oslo-incubator's
version. This syncronizes gettextutils from oslo-incubator commit
997ab277 .

bp user-locale-api

Change-Id: If9cf0c83df6d6c8db844a30c605f60e907abcbdd
Merge "Do not append to messages with +"
Merge "Sync gettextutils from oslo-incubator 997ab277"