Update mdadm to version 4.1 / rev 131 via SR 933225
    
    https://build.opensuse.org/request/show/933225
    by user msmeissn + dimstar_suse
    - Use %{_sbindir} for prerequisite of mkinitrd to work with
      usrmerge of dracut-mkinitrd-deprecated (forwarded request 933221 from suntorytimed)