Problem-1:
When an overlapping lock is issued the merged lock is not assigned the
owner. When flush is issued on the fd, this particular lock is not freed
leading to memory leak

Fix-1:
Assign the owner while merging the locks.

Problem-2:
On fd-destroy lock structs could be present in fdctx. For some reason
with flock -x command and closing of the bash fd, it leads to this code
path. Which leaks the lock structs.

Fix-2:
When fdctx is being destroyed in client, make sure to cleanup any lock
structs.

fixes: #2337
Change-Id: I298124213ce5a1cf2b1f1756d5e8a9745d9c0a1c
Signed-off-by: Pranith Kumar K <pranith.karampuri@phonepe.com>