numademo: free the node_to_use on the way out

Frees pointer node_to_use before exiting program.

Fixes the following valgrind warnings:

  4 bytes in 1 blocks are still reachable in loss record 1 of 1
     at 0x4C28BE3: malloc (vg_replace_malloc.c:299)
     by 0x402973: get_node_list (in /home/sansharm/src/numactl/.libs/numademo)
     by 0x401450: main (in /home/sansharm/src/numactl/.libs/numademo)

Signed-off-by: Sanskriti Sharma <sansharm@redhat.com>

numademo.c

@@ -575,5 +575,6 @@ int main(int ac, char **av)
 			}
 		}
 	}
+	free(node_to_use);
 	return 0;
 }