core: Make antrun plugin version explicit

Currently we don't explicitly specify the version of the maven ant
plugin that we use. This means that we use an old version. This patch
udpates to version 1.7 and makes it explicit in the parent POM.

Change-Id: Id3297da17facdcf72878ecb2891d142a54634dee
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>
(cherry picked from commit 913b958cac7176f965c16524a69e505f7ebe3e46)