* Corner case in which import_role would add another instance of a role with the same signature into roles: when it already existed there.
roles:
- name: a
tasks:
- import_role: name=a
would execute role 'a' 3 times instead of the intended 2 (x2 in roles: phase +1 in tasks:)
* added tests
(cherry picked from commit eca7c3c8c7)
