[vcloud_director] ensure that MetadataEntry is a list
[vcloud_director] Show guest customization "admin password auto"

Guest customization setting "admin password auto" was retrieved but not
shown.
[vcloud_director] Handle Guest admin password

Admin passwords can be retrieved and modified using the VMWare console,
so it's useful to allow the same operations here.

Moreover, when an admin password is enabled and "admin password auto" is
false, it's impossible to modify Guest settings.
i.e., "The administrator password cannot be empty when it is enabled and
automatic password generation is not selected."

This patch also fixes `put_guest_customization_section_vapp` where an
AdminPassword element was never created.
changed __consoles to consoles and renamed consoles method to get_consoles
fixed tests
Add exponential backoff to backoff_if_unfound.
Merge branch 'master' into fixed-xenserver-consoles
fixed consoles to use :aliases
Merge branch 'master' into fixed-xenserver-consoles

Conflicts:
	lib/fog/xenserver/models/compute/server.rb
[xenserver] Adding more XenServer Models
Merge pull request #2467 from zertico/fixed-xenserver-consoles

Fixed bug in XenServer console
Merge pull request #2474 from anl/gce-exponential-backoff

[google|compute] Add exponential backoff to Google Compute Engine's backoff_if_unfound.
Adding more XenServer models
ignore .ruby-version
Forget to reference models on main class
Merge pull request #2480 from alphagov/ruby_version

ignore .ruby-version
Merge pull request #2475 from zertico/adding_more_models

[xenserver] Adding more XenServer Models
expanding/rewriting the getting-help/involved section of README
fix spacing for getting help section of README
Merge pull request #2459 from alphagov/ensure_metadata_entry_is_list

[vcloud_director] ensure that MetadataEntry is a list