symbolic_modes tests occasionally fail on OSX

Errored Tests Cases:

  Test Case tests/resource/file/symbolic_modes.rb reported: #<Beaker::Host::CommandFailure: Host 'nn8elbm0jop4j4t.delivery.puppetlabs.net' exited with 1 running:

 env PATH="/opt/puppetlabs/puppet/bin:${PATH}" ruby -e 'require "etc"; puts (Etc.getgrgid(File.stat("/var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/T/symbolic-modes.XXXXXX.oAsbXzPO/file").gid).name)'

Last 10 lines of output were:

	-e:1:in `getgrgid': can't find group for 719 (ArgumentError)

		from -e:1:in `<main>'>