Correctly set $service_provider
Correctly set $service_provider

The `$service_provider` variable in params.pp is user-definable via `postgresql::globals::service_provider`. Thus params.pp should reference that variable correctly, like other variables from globals.pp.
covermymeds/puppetlabs-postgresql,DavidS/puppetlabs-postgresql,thunderkeys/puppetlabs-postgresql,thunderkeys/puppetlabs-postgresql,covermymeds/puppetlabs-postgresql,javierwilson/puppetlabs-postgresql,kbarber/puppetlabs-postgresql,puppetlabs/puppetlabs-postgresql,npwalker/puppetlabs-postgresql,theforeman/puppetlabs-postgresql,hasegeli/puppetlabs-postgresql,DavidS/puppetlabs-postgresql,fuel-infra/puppetlabs-postgresql,hasegeli/puppetlabs-postgresql,npwalker/puppetlabs-postgresql,tdevelioglu/puppetlabs-postgresql,covermymeds/puppetlabs-postgresql,infoxchange/puppetlabs-postgresql,fuel-infra/puppetlabs-postgresql,puppetlabs/puppetlabs-postgresql,theforeman/puppetlabs-postgresql,PierreR/puppetlabs-postgresql,javierwilson/puppetlabs-postgresql,buzzdeee/puppetlabs-postgresql,PierreR/puppetlabs-postgresql,tdevelioglu/puppetlabs-postgresql,thunderkeys/puppetlabs-postgresql,tdevelioglu/puppetlabs-postgresql,buzzdeee/puppetlabs-postgresql,DavidS/puppetlabs-postgresql,buzzdeee/puppetlabs-postgresql,kbarber/puppetlabs-postgresql,fuel-infra/puppetlabs-postgresql,kbarber/puppetlabs-postgresql,puppetlabs/puppetlabs-postgresql,PierreR/puppetlabs-postgresql,npwalker/puppetlabs-postgresql,hasegeli/puppetlabs-postgresql,infoxchange/puppetlabs-postgresql,theforeman/puppetlabs-postgresql,infoxchange/puppetlabs-postgresql,javierwilson/puppetlabs-postgresql,duritong/puppetlabs-postgresql