Request for review (XXS) : 8067891 Remove vestigal G1SATBCT barrier set kind

[Joseph Provino]

https://bugs.openjdk.java.net/browse/JDK-8067891
Remove vestigal G1SATBCT barrier set kind

G1SATBCT still needs to be defined but there is no concrete class
which uses it.  This means that all instances of

"case BarrierSet::G1SATBCT"

can be removed which is what this change does.

Tested with JPRT.

Webrev:  http://cr.openjdk.java.net/~jprovino/8067891/webrev.01

I will need someone to commit the changes for me.

thanks.

joe