Get the vCenter password from databag for compute

1. Add new attribute openstack_vmware_secret_name to indicate the
databag secret key
2. Get the password from databag if dev mode is false
3. Update the test cases

Implements: blueprint vmware-password-databag

Change-Id: I342e26aee713216f2aecc39113a67ada25ec1fb5
Run nova-manage as correct user/group

We need to explicitly run nova-manage with nova user/group.
Running as root may cause files in /var/log/nova/* to be owned by
root, and this will cause nova services from being able to start (due
to being unable to write to files in that directory).

This is a non-issue when you install from packages as the package
post-install typically does a nova-manage with the correct user, and
this ensures logs are created w/ correct ownership.

Change-Id: Ibe367d95aec5f7b0244812ae67873b5370fc3ae4
Enable instance_name_template configuration

Sometimes the customer want to configure instance name basing on
their own format. So the 'instance_name_template' property should
support to be modified.

Change-Id: I39022c441fdeaf26faee8295dd8719c17dcc03a5
Merge "Get the vCenter password from databag for compute"
improve documentation for miscellaneous config values

Change-Id: I10441aa78a6a11c59e5d7a50ea50740c27196980
Merge "Run nova-manage as correct user/group"
Merge "improve documentation for miscellaneous config values"