Simplify testing RNG code

src/test/test_bitcoin.cpp

@@ -36,8 +36,7 @@ void CConnmanTest::ClearNodes()
     g_connman->vNodes.clear();
 }
 
-uint256 insecure_rand_seed = GetRandHash();
-FastRandomContext insecure_rand_ctx(insecure_rand_seed);
+FastRandomContext insecure_rand_ctx;
 
 extern bool fPrintToConsole;
 extern void noui_connect();