RFR: 7133124 Remove redundant packages from JAR command line

[Rickard Bäckman]

Hi,

We have a problem with some versions of jar reporting errors when trying 
to run jar cf <some.jar> com/test com/test/foo

This fix removes the redundant subdirectories from the command.

Webrev is here:
http://cr.openjdk.java.net/~rbackman/7133124/webrev/

Thanks
/Rickard