(#8147) Change default reporturl to match newer Dashboard versions

Puppet's default reporturl setting was http://localhost:3000/reports, which has
been deprecated in Puppet Dashboard in favor of
http://localhost:3000/reports/upload. As Dashboard is the first-class
destination for the http report processor, this commit changes Puppet's default
to match what current versions of Dashboard expect.

Reviewed-By: Jacob Helwig <jacob@puppetlabs.com>