RFR: 8228394: Cleanup unused java.net SharedSecrets classes

[Claes Redestad]

Hi,

please review this cleanup to remove a few java.net access objects that
are no longer in use.

Webrev: http://cr.openjdk.java.net/~redestad/8228394/open.00/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8228394

(One usage was from sun.misc.ClassLoaderUtil, removed by 
https://bugs.openjdk.java.net/browse/JDK-8034853, which seems
to have forgotten to remove a related and now unused test.jar
file. I removed this too and verified all tests pass.)

Testing: tier1+2

Thanks!

/Claes