Set show_diff to false for Nova SSH private key

The private key is currently being leaked into
the diff output.

Change-Id: I94170f76257c77d1eabeeb3d373c05c50413c53d

manifests/init.pp

@@ -552,6 +552,7 @@ but should be one of: ssh-rsa, ssh-dsa, ssh-ecdsa, ssh-ed25519.")
         mode      => '0600',
         owner     => $::nova::params::user,
         group     => $::nova::params::group,
+        show_diff => false,
         require   => File['/var/lib/nova/.ssh'],
       }
     }

spec/classes/nova_init_spec.rb

@@ -360,6 +360,7 @@ describe 'nova' do
             :mode      => '0600',
             :owner     => 'nova',
             :group     => 'nova',
+            :show_diff => false,
           )
         end
       end
@@ -375,7 +376,7 @@ describe 'nova' do
       it 'should raise an error' do
         expect {
           is_expected.to contain_file('/var/lib/nova/.ssh/id_rsa').with(
-            :content => 'keydata'
+            :content => 'keydata',
           )
         }.to raise_error Puppet::Error, /You must provide both a key type and key data./
       end