requirements.txt: Add keystoneclient
requirements.txt: Add keystoneclient

When running dci-ansible tests in dci-dev-env, we upload files into the
swift. However we're missing the pyhton-keystoneclient leading to
python-swiftclient failing to upload the file.

We don't face this in production car the proper dependencies are in
place at the RPM level.

Change-Id: I111c1c893ff879885bca681dd56013b78e6d0293

enovance/dci-control-server,enovance/dci-control-server,redhat-cip/dci-control-server,redhat-cip/dci-control-server