Fix element miss in client request body

Currently the client sends a request with wrong element name
'os-multiple-create:reservation_id' in the body.
The correct element should be 'os-multiple-create:return_reservation_id'.
The information can be got in this website.
https://wiki.openstack.org/wiki/NovaAPIv2tov3

Change-Id: I7d2f006ef6dbbcd6b41c8adbeee0c0e048d35448
Closes-Bug: #1281342
Re-add install_venv_common to openstack-common.conf

Mistakenly removed it in e0272b0578d2a4f5bd75e68baee1b56f49931266.
Was thrown off by the warning saying module not found, the module is
found on the third try (found in tools).

Change-Id: Iaf5a7ba0259d352cb824b2cdb22291ffb7883efc
Merge "Re-add install_venv_common to openstack-common.conf"
Merge "Fix element miss in client request body"