Tell rsync to preserve hard links for git objects/packs directories

Without -H option the rsync will sync the files that are hardlinked on
the source side as separate files on receiver side. In some situations
this might make it impossible to restore appliance from backup as
restored repository filesystem contents can be several times bigger
than original contents used to create backup.
Merge remote-tracking branch 'kjedruczyk/rsync-hardlinks'