Prefer VERIFY0(n) over VERIFY3S(n, ==, 0)

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #17591

cmd/ztest.c

@@ -8978,7 +8978,7 @@ main(int argc, char **argv)
 		exit(EXIT_FAILURE);
 	} else {
 		/* children should not be spawned if setting gvars fails */
-		VERIFY3S(err, ==, 0);
+		VERIFY0(err);
 	}
 
 	/* Override location of zpool.cache */