RFR: Filter upstream tests for Shenandoah (part 1: tier1_gc)

[Zhengyu Gu]

The patch filters out tier1_gc tests that are not applicable to 
Shenandoah GC. (Pending 
http://mail.openjdk.java.net/pipermail/shenandoah-dev/2018-October/007952.html)

Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/tier1_gc_test/webrev.00/

Test:

   tier1_gc (fastdebug and release) with 
${TEST_VM_OPTS}=-XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC


Thanks,

-Zhengyu