Refactor the way how flavor is chosen for appliance type

[mkasztelnik]

Ugly solution was used to hotfix problem with choosing selected flavor in clew rest api. As a conclusion we added additional database queries (see a672cd9) for details.

Please rethink and refactor choosing flavor mechanism (for sure it should be only in one place). Maybe it can be done using database query?

[mkasztelnik]

If there is not possible to implement it as one DB query than maybe Rails cache can be used to store results of expensive flavor choosing operations? Take a look at http://api.rubyonrails.org/classes/ActiveSupport/Cache/Store.html#method-i-fetch.