HA: timeout for disabling DHCP service during lease synchronization should be controllable
The leases synchronization timeout is now controlled via the 'sync-timeout'. While the synchronization is performed, the DHCP service of the active partner is disabled, but for the hardcoded time of 60 seconds. This should either be the same as the timeout for communication over the control channel or should have its own configuration knob. In fact, when we implement the #5652 we can't really set to the same value as the timeout for communication over control channel, because we will be sending multiple commands but the service should be disabled for the entire synchronization.