tests: make NUTS_PASS use TEST_ASSERT

This will ensure that we fast fail if a test cannot complete,
rather than muddling on and reporting failures elsewhere.

src/testing/nuts.h

@@ -209,7 +209,7 @@ extern const char *nuts_ecdsa_client_crt;
 #define NUTS_PASS(cond)                                              \
 	do {                                                         \
 		int result_ = (cond);                                \
-		TEST_CHECK_(result_ == 0, "%s succeeds", #cond);     \
+		TEST_ASSERT(result_ == 0);                           \
 		TEST_MSG("%s: expected success, got %s (%d)", #cond, \
 		    nng_strerror(result_), result_);                 \
 	} while (0)