packaging: fixes a warning while building

[WARNING]
[WARNING] Some problems were encountered while building the effective
model for
org.ovirt.engine.sdk:ovirt-engine-sdk-java:jar:3.6.0.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for
org.apache.maven.plugins:maven-eclipse-plugin is missing. @ line 143,
column 25
[WARNING]
[WARNING] It is highly recommended to fix these problems because they
threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support
building such malformed projects.
[WARNING]

Change-Id: I2924b7deb5b712e472721ea53bfa8d87513e2516
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>