slapos-testing: don't pin tested eggs

We want the tests to use the code from the repository, but when we have a
pinned version, buildout will use the code from repository only when the
version from the repository match the version spec from the pin.

The way slapos.recipe.template was pinned to 4.4 caused issues when we made
a change in slapos.recipe.template to make it 4.5, because tests were no
longer using code from slapos.recipe.template repository, but from 4.4 egg
from pypi.

To prevent this kind of issues, unset the slapos.recipe.template = 4.4
version pin and also unset the version for all tested egg, to prevent
similar issues if extended profiles also have version pins.