Make wait_for_status robust against multiple calls at different times.

This change removes the dependency between wait_for_status? and
download? by checking for the staged directory if there is the
equivalent of a "cache" miss from the downloader_dict.

I also clean up a previous assumption in the downlaoder.

TEST=Unittests + download followed by wait_for_status with
same archive_url and different.  Got all expected results.
Also ran pylint on both devserver and downloader and fixed a cpl
bugs it caught.

Change-Id: I8c187cd64e40c12442de3e4be8fd4c12db7958f3
Commit-Ready: Chris Sosa <>
Reviewed-by: Chris Sosa <>
Tested-by: Chris Sosa <>
4 files changed