use last parent snapshot

git-svn-id: https://svn.apache.org/repos/asf/maven/indexer/trunk@1428808 13f79535-47bb-0310-9956-ffa450edef68
use build-helper-maven-plugin to allocate server port

git-svn-id: https://svn.apache.org/repos/asf/maven/indexer/trunk@1428809 13f79535-47bb-0310-9956-ffa450edef68
no need of port allocation
use port 0 then get the real local port used.

git-svn-id: https://svn.apache.org/repos/asf/maven/indexer/trunk@1428810 13f79535-47bb-0310-9956-ffa450edef68