Enlarge root disk for m1.tiny flavor.

The default root disk of m1.tiny is 1GB, which is too
small for common images, which causes opaque-to-the-user
boot errors.

Make the root disk of m1.tiny 10GB instead, which is large
enough for most common images.
Merge pull request #222 from blueboxgroup/flavors

Enlarge root disk for m1.tiny flavor.