Only update apt repo list when sources changes
Only update apt repo list when sources changes

Currently Exec[update apt] is "subscribes" to the newrelic apt source file.
However, without the refreshonly parameter set, the Exec will run every time
Puppet is run.

coxmediagroup/puppet-nrsysmond,denmat/puppet-nrsysmond,newrelic/puppet-nrsysmond,coxmediagroup/puppet-nrsysmond,denmat/puppet-nrsysmond,newrelic/puppet-nrsysmond