LU-17276 ldlm: use interval tree for searching in flock

LU-17276 ldlm: use interval tree for searching in flock

This patch converts ldlm_process_flock_lock() to use the new interval
tree to find flock locks more efficiently.

Previously all locks the the same owner were adjacent in the
lr_granted list.  This was used for the second stage of merging
overlapping locks once it was confirmed that there were no conflicts.
Now instead we build up a temporary list of locks in the target range
that have the same owner, and use that for the second stage.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: I0a4f1e833d8db36827c318a020de564a78b0adb5
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53951
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andriy Skulysh <andriy.skulysh@hpe.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>