support: Set proper retransmit timeout for datagram transports

Instead of setting the total timeout and the retransmit timeout to the
same value for datagram transports, use a 1 second retransmit timeout,
so we actually get a retransmit or two before failing.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>