RFR 8224946: jrtfs URI to Path and Path to URI conversions are wrong

[Sundararajan Athijegannathan]

Please review.

Bug: https://bugs.openjdk.java.net/browse/JDK-8224946
Webrev: https://cr.openjdk.java.net/~sundar/8224946/webrev.00/

Earlier attempt for the fix of the same bug resulted in test failures 
and so the fix was reverted. The current webrev has the same fix - but 
fixes 2 jlink tests that used wrong jrt: URI. With this change, internal 
mach5 test run is fine.

Related email threads of earlier fix attempt & reversal:

https://mail.openjdk.java.net/pipermail/core-libs-dev/2019-May/060434.html
https://mail.openjdk.java.net/pipermail/core-libs-dev/2019-May/060459.html

Thanks,
-Sundar