[HBASE-8808] Adding a knob to turn off jacoco

Author: manukranthk

Summary: Adding a skip parameter to skip the jacoco execution.

Test Plan: mvn clean -Dtest=TestSplitLogManager -Dmaven.test.failure.ignore=true -Dhbase.skip-jacoco=true package : No site folder generated.

Reviewers: rshroff

Reviewed By: rshroff

Differential Revision: https://phabricator.fb.com/D866904

Task ID: 2541032

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1497866 13f79535-47bb-0310-9956-ffa450edef68