(maint) Clean up Postgres tests / wait on exts
(maint) Clean up Postgres tests / wait on exts

 - Given before(:all) waits for the puppetdb database to be created in
   Postgres, there's no need for an additional test to verify that
   Postgres is running

 - Restructure the extensions check to make sure it waits for the query
   to have a chance to succeed

puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb