Always write to the filter.xml inside the vaultDir but never to filter-plugin-generated.xml

Currently in case the filter configuration of the plugin has been changed and there is already a filter.xml in the vaultDir this is not being overwritten. Instead a new file named filter-plugin-generated.xml is being generated which is irrelevant for the package (https://github.com/apache/jackrabbit-filevault-package-maven-plugin/blob/15baff9be241a851d4ad36e53336cec1d5613c9d/plugin/src/main/java/org/apache/jackrabbit/filevault/maven/packaging/VaultMojo.java#L372). IMHO this is not a clever default behaviour because it forces to always use mvn clean in case of filter definition changes.

In case someone want's to really manually modify the filter.xml the parameter filterSource should be used instead, but in any case the generated filter.xml inside the vaultDir should contain the latest generated filter file.