hg: jdk9/hs/hotspot: 8161539: 8159666 breaks minimal VM

[calvin.cheung at oracle.com]

Changeset: f184e692e094
Author:    ccheung
Date:      2016-07-21 19:29 -0700
URL:       http://hg.openjdk.java.net/jdk9/hs/hotspot/rev/f184e692e094

8161539: 8159666 breaks minimal VM
Summary: replaces the shouldNotReachHere() with an assert
Reviewed-by: coleenp, dholmes, cjplummer, gziemski

! src/share/vm/oops/instanceKlass.hpp