[8u] RFA for JDK-8147026: Convert an assert in ClassLoaderData to a guarantee

[Shafi Ahmad]

Hi,

Please approve this clean backport [https://bugs.openjdk.java.net/browse/JDK-8147026] to 8u-dev.

Jdk9 Bug: https://bugs.openjdk.java.net/browse/JDK-8147026
Review link: http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2016-February/018010.html
Jdk9 changeset: http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/8341dddb5188

Regards,
Shafi