Remove explicit wrapping of Shellwords.escape in double quotes

According to http://www.ruby-doc.org/stdlib-1.9.3/libdoc/shellwords/rdoc/Shellwords.html#method-c-shellescape

"Note that a resulted string should be used unquoted and is not
intended for use in double quotes nor in single quotes."
Remove expectation of double quotes around environment variables from
test comparisons
Merge pull request #258 from mclazarus/master

Don't quote shell escaped values.