puppet_agent : move *.dll during an upgrade instead of terminating puppet

An upgrade on Windows executes a batch script to execute msiexec, allowing us to terminate the puppet process and unlock and upgrade the DLL files the process holds open. MODULES-4207 moved the puppetres.dll prior to an upgrade to avoid a similar locked file issue.

Could we move all of the DLL files, allowing us to upgrade Windows agents without having to terminate the puppet process, and instead send a signal to the puppet process at the end of the run, matching the behavior of an upgrade on Linux?

https://github.com/puppetlabs/puppetlabs-puppet_agent/blob/master/templates/install_puppet.bat.erb#L43

SET PUPPETBIN=<%= @env_windows_installdir %>\puppet\bin

PUSHD %PUPPETBIN%

REN *.DLL *-%RANDOM%.DLL

DEL /Q *.DLL

POPD

Terminating a puppet run always results in an exit code of 0. This obscures the result of the other changes executed by the run prior to the termination and upgrade. At least one customer depends on the exit code being informative during their provisioning process, during which a puppet run often includes both an upgrade to the puppet agent and other changes.