[docker-syncd-*]: Properly manage syncd with supervisord#617

Merged

jleveque merged 3 commits intosonic-net:masterfrom

jleveque:supervise_syncd

May 24, 2017

Commits on May 20, 2017

Syncd dockers now are built from docker-config-engine instead of docker-base
jleveque
committed
Supervisord in all syncd dockers now call syncd_start.s which is installed by sonic-sairedis repo
jleveque
committed
Update sonic-sairedis submodule
jleveque
committed