Remove copy pasta from plugin agent provider

Commented out, thankfully, but doesn't belong here
New Relic `upgrade_please.key` should always be removed

Part of the process to upgrade to PHP Agent v3
DRY up PHP Agent config to pass variables to template w/ less code

We've already spelled out the attributes in the resource definition, we
can just pass the whole resource in as the `variables`, and have the
template do the heavy lifting, since it's already dealing w/ each
attribute individually.

Template might even be DRY'd up more using some straight Ruby.
Refactor to always set up the newrelic.ini PHP config

Perusing the New Relic docs, it became apparent that the `newrelic.ini`
config should always be in play & configured, even if stating the
`newrelic-daemon` externally. This is because the license key & other
app-level config are set via this file for PHP.