Fix pqueue_test.c memory leak.

Change-Id: I0a93900f0ebb22893d86a454cda086be37d4bbad
Reviewed-on: https://boringssl-review.googlesource.com/1993
Reviewed-by: Adam Langley <agl@google.com>

ssl/pqueue/pqueue_test.c

@@ -76,6 +76,7 @@ static int fixed_random() {
     }
     curr = next;
   }
+  pqueue_free(q);
   return 1;
 }