LU-17216 ofd: make enable_health_write tunable

LU-17216 ofd: make enable_health_write tunable

enable_health_write should be tunable rather than a
compilation option. This allows us to test it more
easily and gives admins the option to try it out
without having to recompile their Lustre servers.
It will still be disabled by default.

Add sanity/70 test to run a simple check to ensure
enable_health_write and health_check don't explode.
It's not a thorough check. But it at least checks
that the interfaces appear to work.

Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I7b1832f8acf578b891386e28c5af760070a6862c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52782
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>