add ability to set api url in template

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
fix missing parts

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
Merge pull request #1448 from vtolstov/simple

builder/digitalocean: add ability to set api url in template