Update warden

$ git shortlog f8768aaa..f7de02ea
Jesse Zhang and Pieter Noordhuis (6):
      Small refactor of drain tests
      Clean up stale jobs when recovering
      Don't call into EM from signal handler
      Refactor tests
      Don't persist stdout/stderr over a restart
      Signal parent after setsid

Kowshik Prakasam and Pieter Noordhuis (8):
      Remove legacy repl (nobody uses it).
      Stop relying on warden-protocol for #type_underscored
      Move repl related files to subdirectory
      Use newer version of warden-protocol
      Fix ReplRunner path in bin/warden.
      Fix and bump warden-client
      Update warden-protocol and warden-client dependencies
      Merge branch 'protocol'

Pieter Noordhuis (14):
      Call out entire namespace in rescue clause
      Use modules instead of classes
      Remove superfluous coding line
      Refactor wrapped request/response into message class
      Import native protocol buffer definitions
      Import generated code
      Fix NetInResponse definition
      Use generated code
      Add comment
      Remove unused code
      Bump warden-protocol version
      Move repl test assets
      Remove #description
      Bump warden-protocol version

Change-Id: I68a74e8086e75423cbf0cf56357ff041fc2abbc9