SUMMARY
After working for some time with http kioslaves and the env setting KDE_FORK_SLAVES=1, I noticed that the helper process kio_http_cache_cleaner was started but not finished. This leads to problems with safely removing the stick for portable installations that were started from a USB stick, for example.

In KDE4 times, this (and other) process(es) were terminated by the `kdeinit4 --shutdown` command after detecting that the main application had been terminated. The listed detection was done by a KDE autostart application called `kwinshutdown` from the package kdebase-runtime, which was started in the background via the automatic execution of `kdeinit` on main application startup. 

For KF5 single application packages on Windows, as currently provided by the KDE CI, there should also be corresponding possibilities to automatically terminate background programs (such as `kio_http_cache_cleaner`) when the main application is terminated.