(MODULES-10651) Add ubuntu 20.04 support

[gimmyxd]

Running unit test with manually bumping facterdb to have Ubuntu 20.04(this will not run in CI until facterdb is released)

on ubuntu-20.04-x86_64
      invalid package_versions
        is expected to raise /invalid version/
        is expected to raise /invalid version/
        is expected to raise /invalid version/
      valid package_versions
        is expected to compile into a catalogue without dependency cycles
        is expected not to raise Exception
        is expected to compile into a catalogue without dependency cycles
        is expected not to raise Exception
        is expected to compile into a catalogue without dependency cycles
        is expected not to raise Exception
        is expected to compile into a catalogue without dependency cycles
        is expected not to raise Exception
      puppet_agent class with install_options with params: {}
        is expected to compile into a catalogue without dependency cycles
        is expected to contain Class[puppet_agent::install] with install_options => ["OPTION1=value1", "OPTION2=value2"]
        is expected to contain Package[puppet-agent] with install_options => ["OPTION1=value1", "OPTION2=value2"]
      puppet_agent class with install_options with params: {:service_names=>[]}
        is expected to compile into a catalogue without dependency cycles
        is expected to contain Class[puppet_agent::install] with install_options => ["OPTION1=value1", "OPTION2=value2"]
        is expected to contain Package[puppet-agent] with install_options => ["OPTION1=value1", "OPTION2=value2"]
      puppet_agent class without any parameters(params: {})
        is expected to compile into a catalogue without dependency cycles
        is expected to contain Class[puppet_agent]
        is expected to contain Class[puppet_agent::params]
        is expected to contain Class[puppet_agent::prepare]
        is expected to contain Class[puppet_agent::install] that requires Class[puppet_agent::prepare]
        is expected to contain Package[puppet-agent] with ensure => "6.5.4-1focal"
        is expected to contain Class[puppet_agent::service] that requires Class[puppet_agent::install]
        is expected to contain Service[puppet]
      puppet_agent class without any parameters(params: {:service_names=>[]})
        is expected to compile into a catalogue without dependency cycles
        is expected to contain Class[puppet_agent]
        is expected to contain Class[puppet_agent::params]
        is expected to contain Class[puppet_agent::prepare]
        is expected to contain Class[puppet_agent::install] that requires Class[puppet_agent::prepare]
        is expected to contain Package[puppet-agent] with ensure => "6.5.4-1focal"
        is expected to contain Class[puppet_agent::service] that requires Class[puppet_agent::install]
        is expected not to contain Service[puppet]
        is expected not to contain Service[mcollective]

Manually tested upgrade from 6.15.0 to a nightly build.