net: vrf: Switch dst dev to loopback on device delete
Attempting to delete a VRF device with a socket bound to it can stall:
unregister_netdevice: waiting for red to become free. Usage count = 1
The unregister is waiting for the dst to be released and with it
references to the vrf device. Similar to dst_ifdown switch the dst
dev to loopback on delete for all of the dst's for the vrf device
and release the references to the vrf device.
Fixes: 2c44df3f81da9 ("net: Introduce VRF device driver") Fixes: cd662513e0037 ("net: Add IPv6 support to VRF device") Signed-off-by: David Ahern <dsa@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>