Use yum as default provider for Amazon platforms

Current Behaviour:

• Due to the fact that Amazon platforms do not have a default provider set, puppet will try to assume what to use which result in trying to install packages using the `gem` provider.

Desired Behaviour:

• Amazon platforms should use `yum` provider

This issue was introduced in PUP-9198 when the yum provider changed from being the default for all redhat osfamilies to only those with OS versions 4-7, as redhat 8 switched to dnf. One unintended consequence was yum was no longer the default provider for amazon since it's osfamily is redhat, but its OS version is 2017.03.