MQTT Schema agent suspend toggle should not be disabled when in error state

### Current Behavior

If the MQTT Agent reports an error then the toggle to suspend is currently disabled.

This means that the agent is running (in its own container on FFC) while failing to connect.

### Expected Behavior

User should be able to suspend (remove the running container) but not delete the data stored against the broker.

### Steps To Reproduce

- create 3rd party broker
- collect topics/payload info
- modify broker settings so it no longer connects
- try to suspend the broker.

### Environment

- FlowFuse version: 2.14.1
- Node.js version: NA
- npm version: NA
- Platform/OS: FFC (and k8s / docker / localfs)
- Browser: NA

### Linked Customers

- Customer name and/or link to HubSpot contact