core: osinfo - missing diskInterfaces for rhel64

* rhel3x64: Added an explicit value for diskInterfaces as it doesn't
  support VirtIO_SCSI.
* rhel4x64 and rhel_5x64 are deriving from rhel_3x64.

Change-Id: I25c764bf07125cc51c7686139e5d1d0ae54f9a28
Signed-off-by: Daniel Erez <derez@redhat.com>