The whole devstack log is written into the console output
(job-output.txt) and into devstacklog.txt.
Remove it from job-output and add a devstack-early log file (same as in
legacy job) that includes all the output of stack.sh.
Make sure the log file is pulled into the stage folder so that it will
end up on logs.o.o.
Change-Id: Ia7c1d8fe5cc03d15f455c6e62ebf4a5f6d62ab1f
b7f8624bed