LU-14149 llite: fiemap set flags for encrypted files

LU-14149 llite: fiemap set flags for encrypted files

FIEMAP ioctl needs to set
FIEMAP_EXTENT_DATA_ENCRYPTED|FIEMAP_EXTENT_ENCODED flags for all
extents of files encrypted by fscrypt.

Also add sanity-sec test_56 to exercise the flags, with just a
plain file layout for now.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I26f788b5c4b37e96de57334f48847b40886e14c2
Reviewed-on: https://review.whamcloud.com/40852
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>