According to here:
http://docs.puppetlabs.com/learning/variables.html
"all facts are strings, and all non-empty strings,
including the string "false" . are true"
Checking "if $::selinux" will always return true,
just like (if 'hello':) in python will always return true.
This uses str2bool to ensure that the variable is evaluated as a boolean.
Change-Id: I9489c3bd9a217c80762f5875f026676268572d79