NFS: Fix attribute bitmask in _nfs42_proc_fallocate()

We can't use nfs4_fattr_bitmap as a bitmask, because it hasn't been
filtered to represent the attributes supported by the server. Instead,
let's revert to using server->cache_consistency_bitmask after adding in
the missing SPACE_USED attribute.

Fixes: 913eca1a

 ("NFS: Fallocate should use the nfs4_fattr_bitmap")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>