Add attach_disconnected flag to postgresql profile

Testing on openSUSE Tumbleweed resulted in the following denial:

apparmor="DENIED" operation="file_mmap" info="Failed name lookup - disconnected path" error=-13 profile="postgresql_akonadi" name="" pid=15531 comm="postgres" requested_mask="wr" denied_mask="wr"

Add the attach_disconnected flag to convert this to a denial we can
handle:

apparmor="DENIED" operation="file_mmap" profile="postgresql_akonadi" name="/" pid=11096 comm="postgres" requested_mask="wr" denied_mask="wr"

... and finally  deny / rw,  because allowing it would be insane and
everything works with the deny rule added.