Expand into file list of jars before passing to class path

Looked like the problem was '<Directory>/*' wasn't enough for classpath to add all the jars in the '<Directory'>

Fix: 
Expands to: 
...
[365] "/usr/lib/hadoop-hdfs//hadoop-hdfs.jar"

Verified on HDP 2.1

library(hdfsc)
> f <- HDFS("/user/ubuntu/passwd", "r")
> d <- read.table(f, stringsAsFactors=FALSE)
> close(f)
> nrow(d)
[1] 134