Remove gettextutils

Since we have now moved to current oslo-incubator code, we can remove
the compatibility code from i18n.py and remove the dropped gettextutils
module from manila.

Adjust manila-share to use i18n code instead of gettextutils.

Change-Id: I5191a1ac068305aee2709b9565b6c1ca2da966a5
Merge "Remove gettextutils"