After upgrading my POMs to sonar-maven-plugin:2.7 the configuration does not work any more. My configuration in settings.xml is like this:
Better than disabling the plugin, you may fix the plugin version to 2.6, which works fine, taking into account sonar.host.url.
For instance, with Maven in my case:
org.codehaus.mojo sonar-maven-plugin 2.6