How can I from the shell remove and apply USB power to one of the host USB ports in my machine?
So it seems that this cannot be done, which I kind of already suspected.
The advice found in some places about echoing
/sys/bus/usb/devices/usb?/power/level does not really remove power from the USB host port, it merely requests the device to go into suspend mode, and vice-versa.
I solved my problem by attaching a USB hub with an external power supply, and then cutting the USB 5V wire in the USB cable going from the host machine to the USB. Then I can turn power on an off from my device via an external power relay connected to the USB hub power supply.
This was asked on Stackoverflow and really should have been migrated here.