[SCB-326] Using the EventManager directly

[zhengyangyong]

…google EventBus because it is good enough

Signed-off-by: zhengyangyong yangyong.zheng@huawei.com

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a JIRA issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a JIRA issue. Your pull request should address just this issue, without pulling in other changes.
• Each commit in the pull request should have a meaningful subject line and body.
• Format the pull request title like [SCB-XXX] Fixes bug in ApproximateQuantiles, where you replace SCB-XXX with the appropriate JIRA issue.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Run mvn clean install to make sure basic checks pass. A more thorough check will be performed on your pull request automatically.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

---

Remove custom EventBus an replace with Already Exists EventManager with google EventBus because it is good enough

[coveralls]

Coverage decreased (-0.04%) to 87.28% when pulling 498ec86 on zhengyangyong:SCB-326 into 769dc9d on apache:master.

[wujimin]

need test
do not merge now.

[zhengyangyong]

Performance test show use custom EventBus has better performance than use EventBus in guava
May cause by guava EventBus invoke subscribe method via java reflection mechanism,need more deep code analysis later
So we do not need merge this PR

	custom EventBus	guava EventBus
tps	1,000,000 +	500,000 +
latency	1ms	1.8ms
consumer cpu	about 650%	about 500%
producer cpu	about 750%	about 800%

more detail can found here (in comments) : https://issues.apache.org/jira/projects/SCB/issues/SCB-326