Connector: Set the CN_NETLINK_USERS correctly

The CN_NETLINK_USERS must be set to the highest valid index +1.
Thanks to Evgeniy for pointing this out.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Cc: stable <stable@kernel.org> [.39]
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>