* [docker-syncd-brcm]: Sleep to allow syncd to create socket before calling bcmcmd
* Instead of fixed sleep interval, continually check for presence of socket
- This PR allows supervisord to log syncd exit events to syslog
- Syncd dockers now are built from docker-config-engine instead of docker-base
- Supervisord in all syncd dockers now call syncd_start.s which is installed by sonic-sairedis repo
- Consolidate config.sh and start.sh scripts into one script (start.sh)
- Solve issue #435 - All dockers now run supervisord as their ENTRYPOINT
- All stdout/stderr output from processes managed by supervisord is now sent to syslog instead of their own files
- Supervisord log messages are now also sent to syslog
- Removed unused smartmontools package from docker-platform-monitor
