DevStack likes to use LC_ALL=en_US.UTF-8 because it does some
post-processing of output that depends on stable sort-order. Pull in
the langpack package that provides this by default -- fedora-minimal
was doing this via yum-minimal so it makes sense to be equivalent.
Change-Id: I799bcfd73e1cb76ee1808b3441f40b0525e3c73d