Unify maven-bundle-plugin version at 2.4.0

This removes superfluous version declarations, fixing about 70 eclipse
warnings. At the same time it bumps the version 2.4.0, to unify it -- we
were using both 2.3.7 and 2.4.0 at the same time.

Change-Id: I0f3f6b68c5c05cb9cc226f75b4eb4dab7d58651d
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "Unify maven-bundle-plugin version at 2.4.0"