[DLM] change lkid format

A lock id is a uint32 and is used as an opaque reference to the lock.  For
userland apps, the lkid is passed up, through libdlm, as the return value
from a write() on the dlm device.  This created a problem when the high
bit was 1, making the lkid look like an error.  This is fixed by changing
how the lkid is composed.  The low 16 bits identified the hash bucket for
the lock and the high 16 bits were a per-bucket counter (which eventually
hit 0x8000 causing the problem).  These are simply swapped around; the
number of hash table buckets is far below 0x8000, making all lkid's
positive when viewed as signed.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>