Replace optional_commands with commands in providers

Optional commands can be used to specify that a
command may not exist when provider suitability
is determined. This is because it may be installed
during the same run where it needs to be used.

Previously, an empty default provider was created
just to prevent failures when provider suitability
was determined. This also required that the provider
be explicitly overridden when the type is used.

Using optional_commands instead of command reduces
the amount of required code. It allows the default
providers to be removed as well as the explicit
provider attributes.

This changed has been implemented for the following
types:
  - nova_manage
  - nova_network
  - nova_admin

lib/puppet/provider/nova_admin/default.rb

@@ -1,16 +0,0 @@
-Puppet::Type.type(:nova_admin).provide(:default) do
-
-  desc "This is a default provider that does nothing. This allows us to install nova-manage on the same puppet run where we want to use it."
-
-  def create
-    return false
-  end
-
-  def destroy
-    return false
-  end
-
-  def exists?
-    fail('This is just the default provider for nova_admin, all it does is fail')
-  end
-end

lib/puppet/provider/nova_admin/nova_manage.rb

@@ -2,9 +2,7 @@ Puppet::Type.type(:nova_admin).provide(:nova_manage) do
 
   desc "Manage nova admin user"
 
-  defaultfor :kernel => 'Linux'
-
-  commands :nova_manage => 'nova-manage'
+  optional_commands :nova_manage => 'nova-manage'
 
   def exists?
     nova_manage("user", "list").match(/^#{resource[:name]}$/)

lib/puppet/provider/nova_network/default.rb

@@ -1,16 +0,0 @@
-Puppet::Type.type(:nova_network).provide(:default) do
-
-  desc "This is a default provider that does nothing. This allows us to install nova-manage on the same puppet run where we want to use it."
-
-  def create
-    return false
-  end
-
-  def destroy
-    return false
-  end
-
-  def exists?
-    fail('This is just the default provider for nova_admin, all it does is fail')
-  end
-end

lib/puppet/provider/nova_network/nova_manage.rb

@@ -2,9 +2,7 @@ Puppet::Type.type(:nova_network).provide(:nova_manage) do
 
   desc "Manage nova network"
 
-  defaultfor :kernel => 'Linux'
-
-  commands :nova_manage => 'nova-manage'
+  optional_commands :nova_manage => 'nova-manage'
 
   def exists?
     begin

lib/puppet/provider/nova_project/default.rb

@@ -1,17 +0,0 @@
-Puppet::Type.type(:nova_project).provide(:default) do
-
-  desc "This is a default provider that does nothing. This allows us to install nova-manage on the same puppet run where we want to use it."
-
-  def create
-    return false
-  end
-
-  def destroy
-    return false
-  end
-
-  def exists?
-    fail('This is just the default provider for nova_project, all it does is fail')
-  end
-
-end

lib/puppet/provider/nova_project/nova_manage.rb

@@ -2,9 +2,7 @@ Puppet::Type.type(:nova_project).provide(:nova_manage) do
 
   desc "Manage nova project"
 
-  defaultfor :kernel => 'Linux'
-
-  commands :nova_manage => 'nova-manage'
+  optional_commands :nova_manage => 'nova-manage'
 
   def exists?
     nova_manage("project", "list").match(/^#{resource[:name]}$/)

manifests/manage/network.pp

@@ -7,7 +7,6 @@ define nova::manage::network ( $network, $available_ips ) {
     ensure        => present,
     network       => $network,
     available_ips => $available_ips,
-    provider      => 'nova_manage',
     notify        => Exec["nova-db-sync"],
   }
 }

manifests/manage/project.pp

@@ -5,7 +5,6 @@ define nova::manage::project ( $owner ) {
 
   nova_project { $name:
     ensure   => present,
-    provider => 'nova_manage',
     owner    => $owner,
     notify   => Exec["nova-db-sync"],
     require  => Nova::Manage::Admin[$owner],