travis: Fix test-queue-worker-reload.
travis: Fix test-queue-worker-reload.

Previously, there were following problems with the implmentation:
* Same file handle was being used to read and write. We used to do
  `seek(0)` and then `read()`. This had a chance to overwrite
  file data. Now we use different file handles to read and write data.
* We were using text streams. Text streams cannot be used with
  `bufferring=0`. Now we use binary streams without buffering so that
  data is available for reading without any delay.

This commit also updates the key(s) that we search in the logfile.
Previously, launch of all queues was announced in the log, now we only
anounce the number of threads that were launched.

This commit also makes sure that we always exit after gracefull shutting
down the development server.

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