[201811][swss][utilities] advance swss/utilities sub modules (#2809)

Submodule src/sonic-swss ae74a27..6e8f991:
  > Create ingress table group during the PFCWD stats list installment (#815)

Submodule src/sonic-utilities 6ba6d27..0f7e75c:
  > If fast-reboot-dump gives an error, don't continue with fast-reboot (#515)

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