Properly detect Linaro (Ubuntu derivative)

This commit sets the os_family grain to 'Debian', thus enabling apt to
be detected as the pkg provider. In addition, it properly sets the
service provider to upstart.
Add note about new mount.unmounted state

This state will not be available until 0.17.0, adding this note so the
docs reflect that.
Merge pull request #6501 from terminalmage/docs

Add note about new mount.unmounted state
Merge pull request #6500 from terminalmage/issue6496

Properly detect Linaro (Ubuntu derivative)