usb-backend: Fix spice-usbredir-redirect-on-connect option
After commit 3e20f17b (cfr "usb-redir: extend USB backend to support emulated devices") this option stopped working, as devices are not redirected. Data for device to guest were not written during initialisation.
With this fix both spice-usbredir-redirect-on-connect and spice-share-cd are working (even together).
This fixes https://bugzilla.redhat.com/show_bug.cgi?id=1874740.
Signed-off-by: Frediano Ziglio freddy77@gmail.com