JRUBY-6970 strikes again. This time patch Dir.glob

I believe this will resolve LOGSTASH-1316 and all related bugs
pertaining to 'pattern not defined' problems caused by JRuby telling
us that __FILE__ is "jar:file:/..." and Dir.glob() isn't capable of
handling that kind of path.
Merge pull request #821 from jordansissel/LOGSTASH-1316

JRUBY-6970 strikes again. This time patch Dir.glob