Convert remaining hypervisors to plugin model

Convert BareMetal, OpenVZ, PowerVM hnd libvirt ypervisor configurations
in Nova to the new plugin setup.

Change-Id: I47d744a2c9fdda0771f5b473ec3b26fb099f7439
Merge branch 'config-local' into dt-test
Merge branch 'fix-get-packages' into dt-test
Merge branch 'hypervisor-others' into dt-test
Merge branch 'ldap-ad' into dt-test