Replace tx node label with proposal in jobs.

Use the proposal node label in place of the old tx node label. The new
proposal.slave host has both labels for the time being, but should
remove 'tx' in the future.

Change-Id: I1899348f0beaaeffcc192b51f90274458b7d3323
Fix logstash.o.o elasticsearch discover node list.

Logstash.o.o needs to be given the host and port for its elasticsearch
discover node list. Fix the change that used just a list of hosts.

Change-Id: If421007f633eb54a5dc65d5ede57d1e0a6f1c5d9
Merge "Replace tx node label with proposal in jobs."
Merge "Fix logstash.o.o elasticsearch discover node list."