nfsd: initialize lease type in nfs4_open_delegation()

While lease is correctly checked by supplying the type argument to
vfs_setlease(), it's stored with fl_type uninitialized. This breaks the
logic when checking the type of the lease.  The fix is to initialize
fl_type.

The old code still happened to function correctly since F_RDLCK is zero,
and we only implement read delegations currently (nor write
delegations).  But that's no excuse for not fixing this.

Signed-off-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>