RFR JDK-8066577: Cleanup and make better use of the stream API in the jrtfs code

[Xueming Shen]

Hi,

This is a aged rfe from Paul's code review comments for the old code. 
base. The
implementation has been changed lots since.  Some has gone, some has 
been updated
accordingly. Just went through the list and here is the change set for 
some minor issues
still present.

issue: https://bugs.openjdk.java.net/browse/JDK-8066577
webrev: http://cr.openjdk.java.net/~sherman/8066577/webrev

Thanks,
Sherman