core.c: In core_process_leave, replace tdelete by tfind/tdelete

tdelete returns a pointer to the parent of the item deleted.

Signed-off-by: Hal Rosenstock <hal@mellanox..com>
access: move minor headers from src/ to include/ folder

Signed-off-by: Sasha Kotchubievsky <sashakot@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>