RFR 8065420: Update test java/net/ResponseCache/ResponseCacheTest.java to eliminate internal API dependency

[Amanda Jiang]

Hi,

May I request your review for following changeset?
There is one networking tests that has dependency on internal API sun.net.www.ParseUtil.
This fix is to remove the internal API dependency from that test.

bug:https://bugs.openjdk.java.net/browse/JDK-8065420
webrev: http://cr.openjdk.java.net/~tyan/amandaj/8065420/webrev.00/

Thanks,
Amanda