generic/45[34]: force UTF-8 codeset to enable utf-8 namer checks in xfs_scrub

generic/45[34]: force UTF-8 codeset to enable utf-8 namer checks in xfs_scrub

The upcoming xfs_scrub tool will have the ability to warn about
suspicious UTF-8 normalization collisions.  We want generic/45[34]
to be able to test this functionality, but to do that we have to
forcibly set the codeset to UTF-8 via LC_ALL since the rest of
xfstests only uses LC_ALL=C.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>