Remove duplicate (identical) maven-jar-plugin to fix Maven WARNING

Remove duplicate (identical) maven-jar-plugin to fix Maven WARNING

[WARNING] Some problems were encountered while building the effective
model for org.opendaylight.genius:mdsalutil-api:bundle:0.4.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.(groupId:artifactId)' must be unique but
found duplicate declaration of plugin
org.apache.maven.plugins:maven-jar-plugin @ line 164, column 15
[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.

Change-Id: I5360209dfbbb0d13ee9e33ffcfc7ff22dd3fcbff
Signed-off-by: Michael Vorburger <vorburger@redhat.com>