qpmulti bench is broken

Somewhere along the way, we got into this:

0.426688 sec to create 1000000 items, 2343634.894569/sec 528000000 bytes

vary size of trie
runtime	elapsed	 load s	 B/item	  items	    mut	tx/loop	 ops/tx	     gc	   txns	    ops	 work s	txns/us	 ops/us	   read	tx/loop	 ops/tx	  Ktxns	   Kops	 work s	txns/us	 ops/us	    raw	   loop
  0.250	  0.250	  0.000	  32.00	     10	      1	      4	      4	      0	  56588	 226352	   0.25	   0.23	   0.92	     31	     32	     32	   5759	 184316	   7.70	   0.75	  23.93	 741.76	 737.14
  0.250	  0.250	  0.000	  17.31	    100	      1	      4	      4	     36	  59708	 238832	   0.25	   0.24	   0.97	     31	     32	     32	   4534	 145114	   7.71	   0.59	  18.82	 583.31	 580.21
  0.250	  0.252	  0.000	  14.70	   1000	      1	      4	      4	    687	  30656	 122624	   0.25	   0.12	   0.49	     31	     32	     32	   4347	 139108	   7.71	   0.56	  18.04	 559.13	 551.02
  0.250	  0.250	  0.001	  15.85	  10000	      1	      4	      4	    529	  14908	  59632	   0.25	   0.06	   0.24	     31	     32	     32	   3654	 116945	   7.72	   0.47	  15.15	 469.75	 467.65
  0.250	  0.250	  0.015	  14.82	 100000	      1	      4	      4	     71	  13328	  53312	   0.25	   0.05	   0.21	     31	     32	     32	   2188	  70018	   7.73	   0.28	   9.06	 280.96	 279.95
  0.250	  0.251	  0.161	  15.12	1000000	      1	      4	      4	      6	   8272	  33088	   0.25	   0.03	   0.13	     31	     32	     32	   1109	  35496	   7.74	   0.14	   4.59	 142.24	 141.27

vary size of trie (readonly)
runtime	elapsed	 load s	 B/item	  items	    mut	tx/loop	 ops/tx	     gc	   txns	    ops	 work s	txns/us	 ops/us	   read	tx/loop	 ops/tx	  Ktxns	   Kops	 work s	txns/us	 ops/us	    raw	   loop
qpmulti: ./src/unix/core.c:270: uv__finish_close: Assertion `handle->flags & UV_HANDLE_CLOSING' failed.
Aborted (core dumped)