Don't allow OPEN of a PseudoFS file

Also, return a better error for nfs_FhandleToCache failures.

Ported from 1.5: 9075bee497b67ec1cd0826cda097d6e0de3cf89a

Signed-off-by: Frank S. Filz <ffilz@us.ibm.com>
Fixed byte range lock merging when up- or downgrading sub-ranges

Ported from 1.5: 44aab46665eee745cda796cd73cd96e34210d644

Signed-off-by: Manfred Haubrich <haubrich@de.ibm.com>
Signed-off-by: Frank S. Filz <ffilz@us.ibm.com>
Fix OPNDG10

Two issues:

1. OPEN CREATE UNGUARDED did not reuse existing state
2. state_share_upgrade did not create union of old access and new access

Signed-off-by: Frank S. Filz <ffilz@us.ibm.com>