contract: avoid going to the DB for entry scripts

This optimizes out DB access for non-deployed contracts under the assumption
that deployed ones are always loaded via `LoadScriptWithHash` (and if they're
not --- it's a bug anyway with the new hashing model) which actually is a very
popular case (every entry script does that).

pkg/core/interop_system_test.go

@@ -581,7 +581,7 @@ func TestContractCall(t *testing.T) {
 
 	runInvalid := func(args ...interface{}) func(t *testing.T) {
 		return func(t *testing.T) {
-			loadScript(ic, currScript, 42)
+			loadScriptWithHashAndFlags(ic, currScript, h, smartcontract.All, 42)
 			for i := range args {
 				ic.VM.Estack().PushVal(args[i])
 			}