Make module behaviour consistent despite value of stringify_facts

[hybby]

Right now, it's possible that the comparison on the $::has_compiler fact may not return the intended result depending on the value of stringify_facts in puppet.conf.

In Puppet 3, this value defaults to true which means all Facts when looked up are passed through #to_s. This means that if the fact has the value of false, it will be considered true when evaluated.

To illustrate this, consider the following:

drew@server# facter -p selinux
false

drew@server# cat /tmp/selinux.pp
if $::selinux {
  notify {"SELinux is enabled":}
} else {
  notify {"SELinux is disabled":}
}

drew@server# grep stringify_facts /etc/puppet/puppet.conf
stringify_facts = true

drew@server# puppet apply /tmp/selinux.pp
<...snip...>
Notice: SELinux is enabled
<...snip...>

If I remember correctly, even blank strings returned from Facter will evaluate to true when flattened.

Since there's already a dependancy on puppetlabs-stdlib, we can use str2bool() to make this backwards compatible. It's a recommended method from Puppet themselves during the upgrade process (source)