Changes to test report directory structure

[Andreas Gustafsson <gson%NetBSD.org@localhost>]

Hi all,

The test reports from bablyon5.netbsd.org have been reorganized into a
subdirectory per year, to avoid running into the filesystem limit of
32766 subdirectories per directory.

This also changes the URL format of the test reports on the web, for example:

  http://releng.netbsd.org/b5reports/i386/build/2017.12.31.11.43.42/test.log ->
  http://releng.netbsd.org/b5reports/i386/2017/2017.12.31.11.43.42/test.log

Historic reports are available using both URL formats to avoid
breaking existing links in mail archives, but new ones will only use
the new format.

The change also affects anyone mirroring the raw test output data from
babylon5 using the public rsync service.
-- 
Andreas Gustafsson, gson%NetBSD.org@localhost