I was told that it is always a good idea to use a bitmap with your mdraids. Mdraid only defaults to "off" because of not wanting to change decades old behavior.

Thus:

• New mdraids should be created with a bitmap.
• There should be no way to switch the bitmap off with Cockpit.
• Mdraids without a bitmap should get a warning and a button to switch it on.

This needs changes to UDisks2 to set the bitmap already during creation. Setting the bitmap location right after creation doesn't work since the array first needs to finish synchronizing.

UDisks2 could just switch its own default, or we could add an option and Cockpit would set that to default. Probably the latter.