NFSv4: Fix fscache cookie aux_data to ensure change_attr is included

Commit 402cb8dd ("fscache: Attach the index key and aux data to
the cookie") added the aux_data and aux_data_len to parameters to
fscache_acquire_cookie(), and updated the callers in the NFS client.
In the process it modified the aux_data to include the change_attr,
but missed adding change_attr to a couple places where aux_data was
used.  Specifically, when opening a file and the change_attr is not
added, the following attempt to lookup an object will fail inside
cachefiles_check_object_xattr() = -116 due to
nfs_fscache_inode_check_aux() failing memcmp on auxdata and returning
FSCACHE_CHECKAUX_OBSOLETE.

Fix this by adding nfs_fscache_update_auxdata() to set the auxdata
from all relevant fields in the inode, including the change_attr.

Fixes: 402cb8dd

 ("fscache: Attach the index key and aux data to the cookie")
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>