Introduce a new "sflow" container (if ENABLE_SFLOW is set). The new docker will include:
hsflowd : host-sflow based daemon is the sFlow agent
psample : Built from libpsample repository. Useful in debugging sampled packets/groups.
sflowtool : Locally dump sflow samples (e.g. with a in-unit collector)
In case of SONiC-VS, enable psample & act_sample kernel modules.
VS' syncd needs iproute2=4.20.0-2~bpo9+1 & libcap2-bin=1:2.25-1 to support tc-sample
tc-syncd is provided as a convenience tool for debugging (e.g. tc-syncd filter show ...)
