[BUG] Newlines are not always properly escaped in domain.yml conversion

[jaX10bt]

Bug description:
If any Rasa response includes newlines (\n\n) and any intent is added to/removed from model or deleted, the domain file gets broken. In these circumstances json_to_yaml_domain in DataMapper conversion controller will turn

text: "new\n\nline"

into

text: |-
  new

  line

Expected behavior:
Newlines inside Rasa responses are always properly escaped when doing json to yaml conversion.

[jaX10bt]

works as intended