Starting with version 15.04, ubuntu is based on systemd. The existing
ubuntu provider did not support systemd.
This commit introduce a new provider dedicated to systemd based
versions.
The previous provider is renamed to ubuntu_upstart.
Provider detection uses the /etc/os=release VERSION_ID.
Version ID is converted to a float value and then used to choose between
providers.
Unit tests are validating the provisioner compatibility.
Fixes#1891
Signed-off-by: Thomas Recloux <thomas.recloux@gmail.com>
Thomas Recloux