releng: Bump maven-resources-plugin to 2.7.

Changelog is
http://jira.codehaus.org/secure/ReleaseNote.jspa?projectId=11145&version=18645
but most important thing is that it will no longer fetch the pre Maven
2.2.1 world.

Change-Id: Ife40d45a025da84a8512afa38165e0a33d229b27
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>
Reviewed-on: https://git.eclipse.org/r/36018
Tested-by: Hudson CI