Make crypto/rng_engine test pass on libressl. Bug not in any released tor.

src/test/test_crypto.c

@@ -147,8 +147,14 @@ test_crypto_rng_engine(void *arg)
 
   /* We should correct the method if it's a dummy. */
   RAND_set_rand_method(&dummy_method);
+#ifdef LIBRESSL_VERSION_NUMBER
+  /* On libressl, you can't override the RNG. */
+  tt_assert(RAND_get_rand_method() == RAND_OpenSSL());
+  tt_int_op(0, ==, crypto_force_rand_ssleay());
+#else
   tt_assert(RAND_get_rand_method() == &dummy_method);
   tt_int_op(1, ==, crypto_force_rand_ssleay());
+#endif
   tt_assert(RAND_get_rand_method() == RAND_OpenSSL());
 
   /* Make sure we aren't calling dummy_method */