LU-16518 lustre: fix implicit-fallthrough warnings

LU-16518 lustre: fix implicit-fallthrough warnings

Explicitly lable switch-case intentional fallthroughs
and reorder cases as needed to silence implicit-fallthrough
warngins as reported by Clang.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I7322b3e4f37bcd1716ca48a31ce698798b58e6cf
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58348
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>