When layoutget returns an entirely new layout stateid it should not
check the generation counter as the new stateid will start with a new
counter entirely unrelated to old one.

The current behavior causes constant layoutget failures against a block
server which allocates a new stateid after an recall that removed all
outstanding layouts.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>