block_resize.cfg: RHEL5 need reboot step in block_resize case

Guest RHEL5 could not detect disk change,
assign need_reboot as yes in the cfg file.

history:
  V2:
    change to RHEL.5 condition
  V1:
    add RHEL and 5 condition lines

Signed-off-by: Xiangmin Han <xhan@redhat.com>