Downgrade aggregator javadoc
Downgrade aggregator javadoc

maven-javadoc-plugin-3.2.0+ does not generate any javadocs, hence we
need a downgraded version.

Change-Id: I7934eea64b81bb4aa1e69aaecc3bffc513db3e0f
Signed-off-by: Robert Varga <91ae5aa8c7a9f7e57b701db766e23e544aaa6ae9@pantheon.tech>

opendaylight/bgpcep