oslo.i18n has recently been released. This patch switches marconi over
oslo.i18n. As per oslo.i18n's instructions, a new i18n module has been
added under marconi. This module defines the translation globals and
imports the necessary functions from oslo.i18n.
The patch doesn't change the way Marconi does translation, this means
that a `_` function is still being injected to the builtins.
Note that the gettextutils module is still a required module from
oslo-inc because there are oslo-inc modules that depend on the old
gettextutils module.
Closes-bug: #1314300
Change-Id: Ifb8f3296d1a0e2483ebd1c8d868b7359ecc99fb5
ef9d5247e9