commit b130ed59 upstream.

Only override netfs->primary_index when registering success.
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>