LU-17043 enc: fix osd lookup cache for long encrypted names

LU-17043 enc: fix osd lookup cache for long encrypted names

Fix osd lookup cache to support files with long encrypted names.
Those encrypted names can be up to 256 bytes, not NUL terminated.

Lustre-change: https://review.whamcloud.com/52016
Lustre-commit: TBD (from 51a526bfa61bb5391a7ac33108e264f590cd3f0c)

Fixes: 07a7befdc1 ("LU-16405 osd: lookup cache")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Ica2329c8a0990395307a14fe9bb9d43db3b364ed
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52017
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>