hg: jdk/hs: 8180709: java -javaagent:agent.jar with run-time that does not contain java.instrument prints confusing error

[chris.plummer at oracle.com]

Changeset: 6e69aea2aee7
Author:    gadams
Date:      2017-12-20 13:41 -0500
URL:       http://hg.openjdk.java.net/jdk/hs/rev/6e69aea2aee7

8180709: java -javaagent:agent.jar with run-time that does not contain java.instrument prints confusing error
Reviewed-by: cjplummer, sspitsyn

! src/hotspot/share/runtime/arguments.cpp
! src/hotspot/share/runtime/arguments.hpp
! src/hotspot/share/runtime/thread.cpp