rszshm: disable valgrind for tests.

It returns EINVAL instead of ENOMEM for test/run.c line 96, then
complains on line 137:

==29368== Invalid read of size 4
==29368==    at 0x4033BC: main (run.c:137)
==29368==  Address 0x400000000018 is not stack'd, malloc'd or (recently) free'd
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/rszshm/_info

@@ -76,6 +76,7 @@
  * 	// $ tail -c +29 /dev/shm/rszshm_LAsEvt/0 | sed 's/./&\n/g' | sort | uniq -c | tr '\n' '\t'; echo
  * 	//  515532 A   527251 B    512930 C    513062 D    544326 E    545876 F    512936 G    522363 H
  *
+ * Ccanlint: tests_pass_valgrind FAIL
  * License: APACHE-2
  * Author: Dan Good <dan@dancancode.com>
  *