LU-11891 utils: getstripe use --mdt-index consistently

LU-11891 utils: getstripe use --mdt-index consistently

LU-10856 fixed most usages of "warning: '-M' deprecated,
use '--mdt-index' or '-m' instead" but missed a few in
cases in sanity test_271d, test_271e, and test_271f.
Fix those tests to use "--mdt-index".

Also, lfs has a few places were the usage of "--mdt-index"
and "--mdt" is inconsistent.  Fix those options to be used
consistently across all commands.

Fixes: 6c617a3d56 ("LU-10856 tests: remove deprecated lfs ...")
Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I013b2198f3a39533da9a0067a0bf5846604b3052
Reviewed-on: https://review.whamcloud.com/34116
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>