staging: lustre: ldlm: reclaim granted locks defensively

It was discovered that to many ldlm locks where being
created on the server side to the point of memory
exhaustion. The work of LU-6529 introduced watermarks
to avoid this memory exhaustion. This is the client
side part of this work for the upstream client.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6529
Reviewed-on: http://review.whamcloud.com/14931
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6929
Reviewed-on: http://review.whamcloud.com/15813


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>