[201811][utilities] advance utilties sub module head (sonic-net#2960)

Submodule src/sonic-utilities 4488525..6b4d1a0:
  > [show vlan brief] Support 'alias' interface naming mode (sonic-net#497)
  > [show interface neighbor expected] Support 'alias' interface naming mode (sonic-net#495)
  > updated show ipv6 interface for alias mode (sonic-net#493)
  > [show] Add serial numbers/uptime/hwinfo to 'show version' output (sonic-net#488)
  > [show] show interface status added vlan and portchannels to command (sonic-net#483)

Signed-off-by: Ying Xie <ying.xie@microsoft.com>