go/zodb: ↑ SNR for ConnOptions

We are going to add more options. Adopt "!" prefix as "no" for
something. Make the code flow in ConnOptions more suitable for further
additions without changing formatter for previous option.

go/zodb/db.go

@@ -99,9 +99,11 @@ func (opt *ConnOptions) String() string {
 
 	s += ", "
 	if opt.NoSync {
-		s += "no"
+		s += "!"
 	}
-	s += "sync)"
+	s += "sync"
+
+	s += ")"
 	return s
 }