Improve openstack Nova plugin

* Mask passwords in configuration files
* Update list of packages for Red Hat distributions
* Update list of files for Red Hat distributions

(GH: #197)

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Signed-off-by: Xavier Queralt <xqueralt@redhat.com>
Fix password protection for nova

Signed-off-by: Xavier Queralt <xqueralt@redhat.com>
Fix configuration files paths for nova

Signed-off-by: Xavier Queralt <xqueralt@redhat.com>