Fails to update the a-r-r file properly when stable branch is used

[Dimitrios Markou]

When the update_ansible_role_requirements() [0] is called to update the SHAs in the a-r-r.yml file when we use a stable version of Openstack it produces a malformed a-r-r.yaml file. An example of this produced a-r-r can be found here [1]. We observe in [1] that the 'keepalived' module has an empty string in the version section.

[0] https://git.openstack.org/cgit/openstack/openstack-ansible/tree/scripts/sources-branch-updater-lib.sh#n223

[1] https://pastebin.com/fPHFgHRF