Enable multiple translation domains for gettextutils

This change set basically addresses the review comments from change
I27640a3c8b255be51bc6396d238098bd25af61ec by allowing multiple domains'
language lists to be cached.

Also remove warning for unused import.

Change-Id: Ia5a6b5dba84c5eb6b1eae7df53fc555843630742
Merge "Enable multiple translation domains for gettextutils"