Crosperf schedv2 (1) - new option and integrating new scheduler.

This Cl introduces a new option '--schedv2' which uses the new
scheduler to allocate jobs (benchmark_runs) to duts.

With this option, schedv2 takes control of storing/allocating jobs and
reimage machines using the new algorithm. This CL leaves actual
reimaging and running jobs non-op (a random time sleep is used for
each such op, which would be replace in later CLs.)

You may try this CL like this and see how schedv2 works -
  crosperf --locks_dir=/usr/local/google/home/shenhan/tmp --use_file_locks=True --logging_level=verbose --schedv2 some.exp

Change-Id: If5bb7751b466c39e54c93fe8f0b4e363be6d9165
Reviewed-on: https://chrome-internal-review.googlesource.com/225515
Commit-Queue: Han Shen <shenhan@google.com>
Tested-by: Han Shen <shenhan@google.com>
Reviewed-by: Han Shen <shenhan@google.com>
diff --git a/image_chromeos.py b/image_chromeos.py
index dd9a336..1d977e0 100755
--- a/image_chromeos.py
+++ b/image_chromeos.py
@@ -50,7 +50,7 @@
 
 
 def DoImage(argv):
-  """Build ChromeOS."""
+  """Image ChromeOS."""
 
   parser = optparse.OptionParser()
   parser.add_option("-c", "--chromeos_root", dest="chromeos_root",