staging/lustre/ldlm: remove server-side congested locks support

This code only makes sense on the server, also while we are at it
drop registration of server-side procfs values and
as all client side values were already moved to sysfs - also
drop now unused procfs helpers.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>