Reset fab connections to openstack so that new connections per session be created when running in parallel mode

In Parallel mode, fab scripts are hung when reusing existing connection by multiple session.
To avoid this, remove the connections to openstack from the connections dict. Now get commands will
create new connections and they independently

Closes-Bug: 1382280

Change-Id: I0a89587eac79d8e1235f492c9454a9c3e088f1b7