Update Karaf validate profile to use Karaf 2.2.2-SNAPSHOT

As Karaf 2.2.2-SNAPSHOT validate plugin has better support to the Karaf feature validation, we should update the validate profile to use it.
Now if you want to validate the change of apache-camel karaf feature, your just need to use this command in the features directory.

  mvn clean install -Pvalidate -Psnapshot

BTW, it should be safe when we release CAMEL 2.8.0.