Don't panic on unexpected messages

This is actually a security bug as it would allow remote triggers
of panics!

daemon/src/maker_cfd.rs

@@ -154,9 +154,9 @@ impl Actor {
             SetupState::Active { taker, .. } => {
                 anyhow::bail!("Currently setting up contract with taker {}", taker)
             }
-            SetupState::None => unreachable!(
-                "`SetupState` is guaranteed to be `Active` before anyone sends a message"
-            ),
+            SetupState::None => {
+                anyhow::bail!("Received setup message without an active contract setup");
+            }
         }
 
         Ok(())

daemon/src/taker_cfd.rs

@@ -220,7 +220,9 @@ impl Actor {
             SetupState::Active { sender } => {
                 sender.send(msg).await?;
             }
-            SetupState::None => anyhow::bail!("OrderAccepted message should arrive first"),
+            SetupState::None => {
+                anyhow::bail!("Received setup message without an active contract setup")
+            }
         }
 
         Ok(())