Added unit tests for the $manage_service functionality

I've added and amended some unit tests in order to check the
$manage_service functionality introduced in previous commits.

spec/unit/classes/smartd_spec.rb

@@ -129,15 +129,15 @@
       let(:params) {{ :ensure => 'absent' }}
 
       it { should contain_package('smartmontools').with_ensure('absent') }
-      it { should contain_service('smartd').with_ensure('stopped').with_enable(false) }
+      it { should_not contain_service('smartd') }
       it { should contain_file('/etc/smartd.conf').with_ensure('absent') }
     end
 
     describe 'ensure => purge' do
       let(:params) {{ :ensure => 'purged' }}
 
       it { should contain_package('smartmontools').with_ensure('purged') }
-      it { should contain_service('smartd').with_ensure('stopped').with_enable(false) }
+      it { should_not contain_service('smartd') }
       it { should contain_file('/etc/smartd.conf').with_ensure('absent') }
     end
 
@@ -165,6 +165,12 @@
       it { should contain_service('smartd').with_ensure('stopped').with_enable(false) }
     end
 
+    describe 'manage_service => false' do
+      let(:params) {{ :manage_service => false }}
+
+      it { should_not contain_service('smartd') }
+    end
+
     describe 'service_ensure => badvalue' do
       let(:params) {{ :service_ensure => 'badvalue' }}