Faster builds

[Michael Schwendt <bugs michael gmx net>]

Some good news for package maintainers with many sub-packages:

Plague used to sleep at least 20 seconds for each (!) file it had to
download from a builder. Even downloading the several small log files used
to take at least 20 seconds *each*.

Reading and debugging the code, I found the source of the problem and
taught the build server to sleep less when files are being downloaded.
Interestingly, the speedup is noticeable even for tiny build-jobs, e.g.

  revisor down from 7m to 4m
  nagios down from 6m to 4m

but it will be incredible for build-jobs with a larger number of pkgs
(e.g. try moodle or nagios-plugins which are in EPEL already). That
means, such packagers get the build-results and the mail notification
much faster.