Use m-site-p 3.3 in ITs to make it M3.1 proof

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1517331 13f79535-47bb-0310-9956-ffa450edef68
Use m-site-p 3.3 in ITs to make it M3.1 proof

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1517332 13f79535-47bb-0310-9956-ffa450edef68