datacenter role fails with oVirt 4.3

[jirimacku]

The ovirt-engine-sdk-python package which contain the ovirtsdk python module is no more installed by default on oVirt 4.3. This causes to fail the role (datacenter, storage) and the whole deploy process.

For use in oVirt 4+ there is new module ovirtsdk4 which is in the python-ovirt-engine-sdk4 package. This package is installed by default with oVirt.

If the ovirt-engine-sdk-python package (with ovirtsdk) is installed outside the role, the particular tasks run just fine.

[fabianvf]

ping @kobihk