puppet_agent install task fails on network hiccups

Description

Out of the 4059 CI runs from the last 7 days , 78 failed to install an agent. That's 1.9% failure rate, which is a big chunk of the environmental failures we see in modules testing.

Looking through the errors, most are from RHEL/yum failing to run properly, followed by a flurry of issues - from timeouts to fileaccess denied - on windows.

See the attached agent_install_failed.json file for a list of all errors.

Expected Behaviour

puppet_agent::install task doesn't fail on insulated network or windows hiccups.

Suggested Mitigation Strategy

The puppet_agent::install task retries downloading/installing the agent in the face of transient network or windows errors to avoid spurious environmental errors becoming customer-visible faults.