net: Initialise init_net.count to 1

Initialise init_net.count to 1 for its pointer from init_nsproxy lest
someone tries to do a get_net() and a put_net() in a process in which
current->ns_proxy->net_ns points to the initial network namespace.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>