[201811][sairedis] advance sairedis submodule head

Submodule src/sonic-sairedis aa092506f..c61d15947:
  > [201811][SAI] move SAI sub module head to v1.4.3 (sonic-net#567)
  > [201811][sai] advance SAI submodule (sonic-net#566)

Signed-off-by: Ying Xie <[email protected]>

Author: yxieca