2.x sync-init doesn't work with PollingDynamicConfig

[brharrington]

When using FixedPollingStrategy it will keep retrying if the syncInit is true and the callback throws an exception. However, PollingDynamicConfig creates a runnable:

    52          strategy.execute(new Runnable() {
    53              @Override
    54              public void run() {
    55                  update();
    56              }
    57          });

That update call catches Exception and doesn't propagate:

    79              try {
    80                  PollingResponse response = reader.call();
    81                  if (response.hasData()) {
    82                      current = response.getToAdd();
    83                      notifyConfigUpdated(this);
    84                  }
    85              }
    86              catch (Exception e) {
    87                  errorCounter.incrementAndGet();
    88                  try {
    89                      notifyError(e, this);
    90                  }
    91                  catch (Exception e2) {
    92                      LOG.warn("Failed to notify error observer", e2);
    93                  }
    94              }