RFR: Demote warning message about OOM-during-evac to informational

[Aleksey Shipilev]

Let's finally do this:

diff -r 8e52377a090e src/hotspot/share/gc/shenandoah/shenandoahConcurrentThread.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahConcurrentThread.cpp	Fri Jan 19 11:38:51 2018 +0100
+++ b/src/hotspot/share/gc/shenandoah/shenandoahConcurrentThread.cpp	Fri Jan 19 11:50:16 2018 +0100
@@ -396,7 +396,9 @@
   if ((! Thread::current()->is_GC_task_thread()) && (! Thread::current()->is_ConcurrentGC_thread())) {
     assert(! Threads_lock->owned_by_self()
            || SafepointSynchronize::is_at_safepoint(), "must not hold Threads_lock here");
-    log_info(gc)("%s. Let Java thread wait until evacuation finishes.",
GCCause::to_string(GCCause::_shenandoah_allocation_failure_evac));
+    log_info(gc)("%s. Thread \"%s\" waits until evacuation finishes.",
+                 GCCause::to_string(GCCause::_shenandoah_allocation_failure_evac),
+                 Thread::current()->name());
     while (heap->is_evacuation_in_progress()) { // wait.
       Thread::current()->_ParkEvent->park(1);
     }

User has nothing to do with that warning, and it is non-user-actionable. So, no point in putting
scary messages in the GC log. It now prints:

[info][gc] GC(63) Concurrent cleanup 611M->611M(1024M) 0.202ms
[info][gc] GC(63) Cancelling concurrent GC: Allocation Failure During Evac
[info][gc] Allocation Failure During Evac. Thread "MyShinyThread" waits until evacuation finishes.
[info][gc] GC(63) Concurrent evacuation 612M->994M(1024M) 315.488ms
[info][gc] GC(64) Pause Full (Allocation Failure) 994M->541M(1024M) 312.493ms

Testing: hotspot_fast_gc_shenandoah

Thanks,
-Aleksey