LU-11518 ldlm: lru code cleanup

LU-11518 ldlm: lru code cleanup

cleanup includes:
- no need in unused locks parameter in the lru policy, better to
  take the current value right in the policy if needed;
- no need in a special SHRINKER policy, the same as the PASSED one
- no need in a special DEFAULT policy, the same as the PASSED one;
- no need in a special PASSED policy, LRU is to be cleaned anyway
  according to LRU resize or AGED policy;

bug fixes:
- if the @min amount is given, it should not be increased on the
  amount of locks exceeding the limit, but the max of them is to
  be taken instead;
- do not do ELC on enqueue if no LRU limits are reached;
- do not keep lock in LRUR policy once we have cancelled @min locks,
  try to cancel instead until we reach the @max limit if given;
- cancel locks from LRU with the new policy, if changed in sysfs;

Signed-off-by: Vitaly Fertman <c17818@cray.com>
Change-Id: I84369da54f680e5fbddd28089c40d1b90722d42d
HPE-bug-id: LUS-8678
Reviewed-on: https://es-gerrit.dev.cray.com/157066
Reviewed-by: Andriy Skulysh <c17819@cray.com>
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Tested-by: Alexander Lezhoev <c17454@cray.com>
Reviewed-on: https://review.whamcloud.com/39560
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>