This commit adds the following new variables to customise whether nova
will allow key/partition/password injection:
nova_libvirt_inject_key
nova_libvirt_inject_partition
nova_libvirt_inject_password
Additionally, the following variable has been added to allow setting
password via Horizon:
horizon_can_set_password
Lastly, password injection can now be tested with tempest via:
tempest_compute_change_password
Note that all variables have been defaulted to their current values.
Closes-Bug: #1469238
Change-Id: Iff434ed7c042f7990990485c34d0f35b9a7baa7a
5bd7a5540c