Cate Desktop hangs when restarted after quit while running a task

[forman]

Expected behavior

When Cate Desktop quits all child process must unconditionally quit too. Cate WebAPI web-service shall always terminate when Cate Desktop terminates.

Actual behavior

Cate Desktop hangs when restarted after quit while running a task. Under some circumstances, the Cate web-service process stays alive after Cate Desktop quits. The Cate web-service may become unresponsive (e.g. due to high CPU loads while processing data or swapping large RAM amounts or downloading data) thus wont recieve a stop request form Cate Desktop when it quits. In this case, a child process remains alive while Cate Desktop has already terminated.

Starting Cate Desktop a second time will cause it to hang, waiting for the existing web-service to connect infinitely.

Steps to reproduce the problem

1. Start Cate Desktop
2. Perform long-running task (e.g. ODP download, or animate_map op on large dataset)
3. Quit Cate Desktop
4. Start Cate Desktop

--> Will wait forever connecting to Cate service

Specifications

Cate Desktop up to 2.0.0.dev7