Currently the devel packages are installed everywhere,
but they only need to be where the wheels are built.
Also, there is already a task to install the packages
needed on the target hosts when installing - so we do
not need to give the same list to the venv install role
because they will already have been installed.
Finally, we remove the unnecessary installation of the
compiling packages because the python venv build role
already does it.
Depends-On: https://review.openstack.org/613585
Change-Id: I78a0df7ba62b59ea63ddceb76d47c9422235b9f3
c1e3248373