backuppc: Fix depency error from .ssh directory when $backuppc_datadir is not defined.

backuppc/manifests/init.pp

@@ -202,6 +202,7 @@ class backuppc::server {
         mode    => "0750",
         owner   => "root",
         group   => "backuppc",
+        require => Package["BackupPC"],
     }
     file { "/var/lib/BackupPC/.ssh/id_rsa":
         ensure  => present,