Currently the install task fails with:
The conditional check 'nova_get_venv | failed or nova_get_venv | skipped' failed.
This is due to the fact that these registered vars are no longer
present, since https://review.openstack.org/599240 removed them.
Rather than have a seperate task to install the extra package,
we can consolidate it into the common task with the same
conditionals.
Change-Id: I41becf0edc25a4b5ea59cb1559facded32f0bbf9