Fix 'glance-cache-manage -h' default interpolation

Some options were showing up as %(default)s when running
"glance-cache-manage -h".

Fixes bug 1197472

Change-Id: I1c7586cbc52445e3bdca28a71378f40ecb5b07a9
Sync gettextutils from oslo

Bring in the necessary code for handling Glance translations

Partially implements bp user-locale-api

Change-Id: I5bc88e018c915d177560bcd42bd5733675e59516
Merge "Fix 'glance-cache-manage -h' default interpolation"
Merge "Sync gettextutils from oslo"