LU-15420 llite: cleanup ll_lookup_it()

LU-15420 llite: cleanup ll_lookup_it()

Newer kernels use fscrypt_prepare_new_inode() to enquire if the
inode is really encrypted. The current Lustre stack is not
setup for this. Much of the fscrypt handling happens at the
top of the basic VFS operation hooks. Rework the stack to
move this handling deeper into tha stack to the level of the
function ll_lookup_it(). This change also cleans up the code
greatly.

Change-Id: I803751759aa954403dd802f7277e870c1f9cd6da
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56233
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>