[Feature Request] increase reconnect timeout automatically if reconnection timed out

[zhangzujian]

For large scale ovsdb servers, a common timeout, e.g. 3s, is not enough when the client has monitors and the monitor method is ConditionalMonitorRPC.

We can introduce a new feature which increases the timeout automatically if last reconnection timed out, like exponential backoff does.

libovsdb keeps reconnecting to NorthDB every 4 seconds