Cycles: Properly free memory used by KernelGlobals

Previous logic did not free memory used by vector classes
which were storing images, causing memory leaks.

intern/cycles/device/device_cpu.cpp

@@ -702,6 +702,7 @@ public:
 		}
 
 		thread_kernel_globals_free((KernelGlobals*)kgbuffer.device_pointer);
+		kg->~KernelGlobals();
 		mem_free(kgbuffer);
 		delete split_kernel;
 	}