RFR(s): 8148239: TestSelectDefaultGC.java incorrectly expects G1 on non-server class machines

[Per Liden]

Hi,

The TestSelectDefaultGC incorrectly assumes that "Server VM" means it's 
running on a server class machine. This patch removes that assumption 
and instead explicitly passes AlwaysActAsServerClassMachine and 
NeverActAsServerClassMachine to the VM to influence the machine type and 
in turn the default GC selection.

Bug: https://bugs.openjdk.java.net/browse/JDK-8148239
Webrev: http://cr.openjdk.java.net/~pliden/8148239/webrev.0/

thanks,
Per