Re-enable lazy translation

Re-enable lazy translation

This patch re-enables lazy translation to enable REST API
responses to be translated to the requested locale (I.E. setting
'Accept-Language: zh-CN'.)

This patch also removes the unnecessary manual import of
'cinder.openstack.common.gettextutils _' in Cinder code.  Since _ is
still being imported in the cinder.openstack.common files from Oslo
we still need to set gettexttutils.enable_lazy().  enable_lazy will
be able to be removed once the manual imports of _ have been removed
from Oslo.

implements-bp: i18n-messages
Change-Id: I0b5a35a2cc28d97d12ceccccd58565b487fef428