staging: lustre: llite: normal user can't set FS default stripe

Current client doesn't check permission before updating filesystem
default stripe on MGS, which isn't secure and obvious.

Since we setattr on MDS first, and then set default stripe on MGS,
we can just return error upon setattr failure.

Now filesystem default stripe is stored in ROOT in MDT, so saving
it in system config is for compatibility with old servers, this
will be removed in the future.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8454
Reviewed-on: http://review.whamcloud.com/21612
Reviewed-on: http://review.whamcloud.com/22580


Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>