svc/conntrack.in: Leave time for network configuration to settle.

svc/conntrack.in: Leave time for network configuration to settle.

Introduce new machinery to delay `kicking' the peer configuration.

  * Changes as a result of reports from NetworkManager and similar are
    now delayed, currently by 2s.  Further reports restart the delay, so
    we update 2s after the last report in a sequence.  This long delay
    is unfortunate, but necessary according to my experiments.

  * The 30s interval timer no longer does anything if a kick is
    scheduled but delayed.

  * Kicks resulting from initial state inspections aren't delayed;
    neither are direct user requests via the `up' and `down' commands.