8005857: assert in GC_locker from PSOldGen::expand with -XX:+PrintGCDetails and Verbose

Summary: Use GC_locker::is_active_and_needs_gc() instead of GC_locker::is_active() for providing information about the reason of heap expansion.
Reviewed-by: jmasa, johnc

src/share/vm/gc_implementation/parallelScavenge/psOldGen.cpp

@@ -256,7 +256,7 @@ void PSOldGen::expand(size_t bytes) {
   }
 
   if (PrintGC && Verbose) {
-    if (success && GC_locker::is_active()) {
+    if (success && GC_locker::is_active_and_needs_gc()) {
       gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead");
     }
   }