[SMB3] Add parsing for new mount option controlling persistent handles

"nopersistenthandles" and "persistenthandles" mount options added.
The former will not request persistent handles on open even when
SMB3 negotiated and Continuous Availability share.  The latter
will request persistent handles (as long as server notes the
capability in protocol negotiation) even if share is not Continuous
Availability share.

Signed-off-by: Steve French <steve.french@primarydata.com>
Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>