Network attach/detach can assign the IP to any node, including the same
node it got detached from.
If ip gets assigned to different node:
- Client contacts the new node and the epoch from clientid is going to
  differ from that of the server node's. In this case server returns
  STALE_CLIENT_ID and forces client to reclaim their locks.
- If the ip gets assgined to same node, epochs are going to be same
  and server can't find the clientid in its hash table. This results in
  EXPIRED_CLIENT_ID and forcing client not to reclaim. The fix is for
  this case.

Fix: Keep the clientid in the hash table marking it stale. On the first
  attempt to use that client id, delete it from the hash and return
  STALE_CLIENT_ID, this allows client to reclaim locks after
  establishing new clientid.

Signed-off-by: Venkateswararao Jujjuri "<jvrao@linux.vnet.ibm.com>