I'd like to consider two things:
1. Put the metadata key in the actual option name
2. Make the X-CondtitionMachineMetadata* keys take a single string, breaking apart multiple values across multiple lines

```
X-ConditionMachineMetadataRegion=us-east-1
X-ConditionMachineMetadataRegion=us-west-1
X-ConditionMachineMetadataHostType=ssd
```

Thoughts?