Change unit string translation in volume limit templates

This fixes an issue where the lazy translated "GB" unit string is
not properly resolved in the volume limit templates. This error
does not happen in a devstack environment but has been found to
happen in chef and puppet deployed OpenStack production
environments.

Closes-Bug: 1332238
Change-Id: Icc056ca508f430e981049ca00985d329c92a6ab4
Merge "Change unit string translation in volume limit templates"