[8] RFR: Fix tier2_gc_shenandoah group definition

[Aleksey Shipilev]

A trivial thing that happened back in 2018 during test configs backports:

diff -r 7f027e9c4a4b test/TEST.groups
--- a/test/TEST.groups  Fri Feb 28 17:59:50 2020 +0100
+++ b/test/TEST.groups  Mon Mar 02 11:18:21 2020 +0100
@@ -150,5 +150,5 @@
   gc/startup_warnings/TestShenandoah.java \
   gc/shenandoah/jvmti/TestGetLoadedClasses.sh \
-  gc/shenandoah/
+  gc/shenandoah/ \
   -gc/shenandoah/TestStringDedupStress.java \
   -gc/shenandoah/jni/TestCriticalNativeStress.sh \

Missing backslash makes jtreg ignore the rest of the block, and print the warning message.

11u has it right, jdk/jdk has it right, but not 8u.

Testing: hotspot_gc_shenandoah

-- 
Thanks,
-Aleksey