JAV-546 register an anonymous subscriber to listen to instance registry event and trigger AFTER_REGISTRY event

[yhs0092]

I've thought about several solutions on this issue.

• move sending AFTER_REGISTRY logic into ServiceCenterTask. But this means ServiceCenterTask need to get the instance of CseApplicationListener, and triggerEvent() of CseApplicationListener has to be changed to public.
• move sending AFTER_REGISTRY logic into a call-back function and pass it to ServiceCenterTask. When instance registry is completed, this function should be called. But this will change several Class from RegistryUtils to ServiceCenterTask.

I think both of them are not good. So I choose to write an anonymous subscriber and let it to listen to MicroserviceInstanceRegisterTask. Maybe this is the solution with the minimum change of code.

[coveralls]

Coverage decreased (-0.01%) to 86.906% when pulling bad5fe8 on yhs0092:JAV-546_set_After_Registry_Trigger_Time into 7e4bbc4 on ServiceComb:master.

[wujimin]

it's better to write new comments in english.
and maybe this logic can be a new method, only invoke in this place.

[yhs0092]

I've extracted this part into a new private method, and translated the comments into English. Please review it.

[coveralls]

Coverage decreased (-0.01%) to 86.907% when pulling 33e793d on yhs0092:JAV-546_set_After_Registry_Trigger_Time into 7e4bbc4 on ServiceComb:master.