Fix various pom issues

Mark some jars as only used for tests so they don't go into
the shaded jar.

Standardize on the 2.9.2 version of kafka since that is what
monasca-common uses

Remove the extra declaration of the maven clean plugin that I
put in

Change-Id: I2df38b53ba3baed8558a62dfe7de74f305f8172a