(#12452) Make Puppet::Util::SELinux#read_mounts work on Ruby 1.9
There's no String#collect in Ruby 1.9. #each_line works in both 1.8 and 1.9,
and I think better captures the intent of what we were trying to do anyway.
Signed-off-by: Deepak Giridharagopal <deepak@puppetlabs.com>