[430527] Move the p2 metadata goal into pluginManagement

Bug: 430527
Change-Id: I67e171caeef5e03383093d905011a01c7d505e26
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
[430527] Fix malformed POM

Bug: 430527
Change-Id: I33e9cd6dd1f3cda501b7656de9e719dd89a950af
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>