[Submodule update] sonic-swss

[portsorch] add buffer drop FC group 
[bitmap_vnet] Fix VNET route priority issue (sonic-net#1421)
[vnet] Maintain the reference count of the nexthop when creating a
vn… (sonic-net#1414)
[intfsorch] Retrieve Port object before setting NAT zone on router
interfaces. (sonic-net#1372)