RFR: 8021588 : (s) Remove explicit othervm execution from jdk/test/Makefile

[Mike Duigou]

Hello all;

I heard word from Alan Bateman that the jdk/test/TEST.ROOT includes accurate specification of which tests cannot be run by JTReg in agentvm mode. ie. they require othervm mode. I tested out removing the duplicate othervm specification from the jdk/test/Makefile and everything still seems to run. 

http://cr.openjdk.java.net/~mduigou/JDK-8021588/0/webrev/

Removes othervm specifications from the test/Makefile and other resulting simplifications.

This lets us further simplify the jdk/test/Makefile and removes needless duplication. Great!

I've been playing with another change inspired by work done by Tim Bell. When running tests concurrently it helps to specify -XX+UseSerialGC to avoid over creation of GC threads for what are mostly short lived tests. Testing jdk_utils on my 24 core / 32GB dev box using serial GC provides about 5%-10% speedup and appears to reduce memory usage by 20% or more. Unfortunately there are a few tests in java.lang.manangement which explicitly request incompatible GC options. I haven't figured out yet how to allow these tests to override the -XX+UseSerialGC vmoption in a sane way. (I can think of several rude ways to do it). So for now, this change is commented out.

Mike