Before this change, only the ansible_local provisioner supported this
option (for ansible version requirement, and pip installation). Now, the
ansible host-based provisioner can also require a exact ansible version.
Resolve#8914
Note: this has been added as part of #6570 resolution, since the
introduction of the `compatibility_mode` auto-detection made both
provisioners made capable to detect ansible version.
Pending: optimize the code to avoid duplicated executions of "ansible
--version" command.
8c0df3d046