Workaround ansible bug where access var via dict doesn't get real value (#1912)

* Change deprecated vagrant ansible flag 'sudo' to 'become'

* Workaround ansible bug where access var via dict doesn't get real value

When accessing a variable via it's name "{{ foo }}" its value is
retrieved. But when the variable value is retrieved via the vars-dict
"{{ vars['foo'] }}" this doesn't resolve the expression of the variable
any more due to a bug. So e.g. a expression foo="{{ 1 == 1 }}" isn't
longer resolved but just returned as string "1 == 1".

* Make file yamllint complient