8048088: Conservative maximum heap alignment should take vm_allocation_granularity into account

Summary: Also consider os::vm_allocation_granularity in the calculation.
Reviewed-by: brutisso

src/share/vm/runtime/arguments.cpp

@@ -1505,8 +1505,10 @@ void Arguments::set_conservative_max_heap_alignment() {
     heap_alignment = G1CollectedHeap::conservative_max_heap_alignment();
   }
 #endif // INCLUDE_ALL_GCS
-  _conservative_max_heap_alignment = MAX3(heap_alignment, os::max_page_size(),
-    CollectorPolicy::compute_heap_alignment());
+  _conservative_max_heap_alignment = MAX4(heap_alignment,
+                                          (size_t)os::vm_allocation_granularity(),
+                                          os::max_page_size(),
+                                          CollectorPolicy::compute_heap_alignment());
 }
 
 void Arguments::set_ergonomics_flags() {