Build mirror using proper requirements.

* tools/integration.sh: Use the --no-update flag to run-mirror to make
sure that the repo checked out by devstack-gate is the repo used to
build the mirror. Otherwise `git reset --hard remote/origin/master` is
used which we do not want. Also, we can't update the requirements repo
until integration.sh is working and for that we need to install d2to1
into the mirror. Usually this would require a requirements repo change,
but chicken and egg. Force it in along with pip and setuptools instead.
This can be removed when d2to1 is added to the requirements repo.

Change-Id: Id5c2c902832e475f28310fdd547672464bf42c0c