EX-9372 lpurge: rid of dup layout get

EX-9372 lpurge: rid of dup layout get

Delete the unnecessary lpurge_mirror_delete() repeat layout getting
code, and update fd/fdv open flags align with LU-14677 to allow
layout operations on encrypted files, even when the encryption key
is not available.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: If4e6e3a9c46ab782f08e5bc5b3710339af051719
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54527
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Alexandre Ioffe <aioffe@ddn.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandre Ioffe <aioffe@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>