Improve test logging

* split log file for parallel tests using format
  'check-all-${plugin}-${testname}.log'
* write START/REAP marks alongs the test output
* check-all executable use 'check-all.log' or
  standard output in verbose mode

Change-Id: Idc94defc8133556c044334269e26493cbcc9d5c4
Reviewed-on: http://review.couchbase.org/28255
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>