Parameterize WaitForExit for PXP agent in Puppet_agent module

Basic Info

Module Version: 2.2.1
Puppet Version: any Puppet version
OS Name: Windows

Actual Behavior:

/files/install_puppet.ps1 script currently doesn't accept a parameter and is bound by the hard coded value of 2 minutes (12000 ms). When a Puppet Run exceeds 2 minutes this causes the script to fail and write the following message to the logs: "ERROR: Timed out waiting for pxp-agent!"

Created the following PR to add this as a parameterization to the module and script: https://github.com/puppetlabs/puppetlabs-puppet_agent/pull/436

Desired Behavior: 

As a user, I would like to be able to change the timeout value by setting it as a parameter and if not defined, use the default value of 2 minutes.