[HBASE-8808] Enabling the code coverage tool jacoco into maven.

Author: manukranthk

Summary: Modifying the pom.xml to include jacoco into maven

Test Plan: Run "mvn clean package" and verify the code coverage report is generated.

Reviewers: liyintang

Reviewed By: liyintang

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D864255

Task ID: 2541032

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1497033 13f79535-47bb-0310-9956-ffa450edef68