LU-8191 mdt: convert functions to static

LU-8191 mdt: convert functions to static

Static analysis shows that a number of functions
could be made static. This patch declares several
functions in mdt_coordinator.c static.

 mdt_coordinator.c:2145:9: warning: Should this function be static?
 ssize_t loop_period_show(struct kobject *kobj,
         ^

Further patches will follow to clean up the
remaining non-static functions in other subsystems.

Lustre-change: https://review.whamcloud.com/51345
Lustre-commit: a1d332f613ac41f4a565c3aeca6633fbd618467e

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I0350b0d5c88c0a8d1f1748d1d429cdf90afb96b7
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54602
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>