RDS: TCP: Retransmit half-sent datagrams when switching sockets in rds_tcp_reset_call...

RDS: TCP: Retransmit half-sent datagrams when switching sockets in rds_tcp_reset_callbacks

Orabug: 23542064

Backport of upstream commit 0b6f760cff04 ("RDS: TCP: Retransmit half-sent
datagrams when switching sockets in rds_tcp_reset_callbacks")

When we switch a connection's sockets in rds_tcp_rest_callbacks,
any partially sent datagram must be retransmitted on the new
socket so that the receiver can correctly reassmble the RDS
datagram. Use rds_send_reset() which is designed for this purpose.

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>