solrj.4.6.0 has a bug which prevents the attachment of a remote solr (as
tested with a SolrCloud). See bug report
https://issues.apache.org/jira/browse/SOLR-5532
This bug shall be fixed in Solr 4.6.1.
Fortunately, solrj-4.5.1 works together with solr-4.6.0 thus the current
index does not need to be changed.