xprtrdma: Reset connection timeout after successful reconnect

If the new connection is able to make forward progress, reset the
re-establish timeout. Otherwise it keeps growing even if disconnect
events are rare.

The same behavior as TCP is adopted: reconnect immediately if the
transport instance has been able to make some forward progress.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>