recipe: add tests
recipe: add tests

Add tests for recipe parsing.
Covered:
- YAML syntax
- templating mechanism
- 'sector' function

$ go test -coverprofile=cover.out ./
ok  github.com/go-debos/debos/recipe 0.011s  coverage: 94.7% of statements

Signed-off-by: Denis Pynkin <3fbf95ee68899518ee8799d35f88c8f7982aa936@collabora.com>

go-debos/debos,d4s/debos