hg: jmc/jmc: JMC-6161: Getting the p2-maven plug-in from maven central, making jmc buildable again

[marcus.hirt at oracle.com]

Changeset: 2177c12e7894
Author:    hirt <marcus.hirt at oracle.com>
Date:      2018-10-10 15:18 +0200
URL:       http://hg.openjdk.java.net/jmc/jmc/rev/2177c12e7894

JMC-6161: Getting the p2-maven plug-in from maven central, making jmc buildable again
Summary: The reficio maven repo doesn't seem to be up anymore, and there is a released version of it on maven central
Reviewed-by: mwengner

! releng/third-party/pom.xml