LU-18162 mdc: convert Metadata Client to LU device

LU-18162 mdc: convert Metadata Client to LU device

Convert MDC to use LU device init/fini rather
than the legacy OBD API.

Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Ic48accf1104d2845707b44519c32c5ced56ae8ef
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58809
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>