[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.

lib/fog/vcloud_director/README.md

@@ -387,6 +387,7 @@ vm.customization
     join_domain_enabled=false,
     use_org_settings=false,
     admin_password_auto=false,
+    admin_password='',
     admin_password_enabled=false,
     reset_password_required=false,
     virtual_machine_id="2ddeea36-ac71-470f-abc5-c6e3c2aca192",

lib/fog/vcloud_director/models/compute/vm_customization.rb

@@ -15,6 +15,7 @@ module Fog
         attribute :join_domain_enabled
         attribute :use_org_settings
         attribute :admin_password_auto
+        attribute :admin_password
         attribute :admin_password_enabled
         attribute :reset_password_required
         attribute :virtual_machine_id

lib/fog/vcloud_director/parsers/compute/vm_customization.rb

@@ -32,6 +32,8 @@ module Fog
               @response[:join_domain_enabled] = (value == "true")
             when 'UseOrgSettings'
               @response[:use_org_settings] = (value == "true")
+            when 'AdminPassword'
+              @response[:admin_password] = value
             when 'AdminPasswordEnabled'
               @response[:admin_password_enabled] = (value == "true")
             when 'AdminPasswordAuto'

lib/fog/vcloud_director/requests/compute/put_guest_customization_section_vapp.rb

@@ -62,6 +62,7 @@ module Fog
             :change_sid => :ChangeSid,
             :join_domain_enabled => :JoinDomainEnabled,
             :use_org_settings => :UseOrgSettings,
+            :admin_password => :AdminPassword,
             :admin_password_enabled => :AdminPasswordEnabled,
             :admin_password_auto => :AdminPasswordAuto,
             :reset_password_required => :ResetPasswordRequired,