Fix the online status in OpsWorks

When an instance is running, OpsWorks reports its status as "online"
[1], while EC2 reports it as "running". Until now, moto copied the EC2
instance's status as is. This commit introduces the converts the running
status to online when returned by OpsWorks.

[1]: https://docs.aws.amazon.com/cli/latest/reference/opsworks/describe-instances.html

moto/opsworks/models.py

@@ -125,6 +125,9 @@ class OpsworkInstance(BaseModel):
     def status(self):
         if self.instance is None:
             return "stopped"
+        # OpsWorks reports the "running" state as "online"
+        elif self.instance._state.name == "running":
+            return "online"
         return self.instance._state.name
 
     def to_dict(self):