xfsprogs: Fix uninitialized cfg->lsunit

xfsprogs: Fix uninitialized cfg->lsunit

While investigating another mkfs bug, noticed that cfg->lsunit is sometimes
left uninitialized when it should not.  This is because calc_stripe_factors
in some cases needs cfg->loginternal to be set first.  This is done in
validate_logdev. So move calc_stripe_factors below validate_logdev while
parsing configs.

Signed-off-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>