8043086: Hotspot is expected to report OOM which is occurred String.intern(), but crashes in JDK8u5

Summary: In case of allocation failure, restore the value of _chunk in Arena
Reviewed-by: dholmes, dcubed

src/share/vm/memory/allocation.cpp

@@ -561,6 +561,7 @@ void* Arena::grow(size_t x, AllocFailType alloc_failmode) {
   _chunk = new (alloc_failmode, len) Chunk(len);
 
   if (_chunk == NULL) {
+    _chunk = k;                 // restore the previous value of _chunk
     return NULL;
   }
   if (k) k->set_next(_chunk);   // Append new chunk to end of linked list