Fix rtd verify for lftools

Fix rtd verify for lftools

lftools docs build runs literal lftools commands
these commands are only avaliable if the current patchset
is installed.

this part is a bit of a hacke, suggestions welcome.
also, if anyone knows how this ever worked before,
id love to know.

Also, install tox so that path has python 3 version of tox
first in path.

Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>
Change-Id: Ic3f9bd788db851bec815e86d57a1788e7eae945a