Bump src/switchboard/src/github.com/pivotal-cf-experimental/switchboard

Use a config file to describe switchboard backends instead of arg list

[#82968904]

Bump :
  Abhijit Hiremagalur:
     Use config.Backend directly, avoid primitives
  Abhijit Hiremagalur and Asim Praveen:
     Revert to uint in millis for healthcheck timeout
     Make pidFile a flag to set it from ctl script
     Backfill tests for basic error handling when loading config
     Use assertion for error checking since this is a spec
     Use go style duration instead of uint to represent millis
     Avoid hardcoding /tmp for better test isolation
     Extract loading of config file to config package
     Extract config out of main
     Move flags to config file