The value returned by this function will be one of (if no lease break is pending):
F_RDLCK to indicate a shared lease is held.
F_WRLCK to indicate an exclusive lease is held.
F_UNLCK to indicate no lease is held.
(if a lease break is pending):
F_RDLCK to indicate an exclusive lease needs to be changed to a shared lease (or removed).
F_UNLCK to indicate the lease needs to be removed.