crit if "extra_roles" exist

[trombik]

extra_roles had been used to git submodule $DEPENDED_ROLE when requirements_path does not exist. it is now deprecated and should not exist. the depended roles are:

• automatically downloaded, when the role is used in a project
• automatically downloaded when the role is tested by kitchen and requirements_path is set
• automatically downloaded by .travis.yml, and extra_roles is created in the process

so, there is no reason for it to be in a repository.