Some more static analyzer issue fixes
Fixes the following issues:
- src/usb-device-widget.c:224: leaked_storage: Failing to save or free storage allocated by "g_path_get_basename(filename)" leaks it.
- src/usbutil.c:148:52: warning: Use of zero-allocated memory
- src/channel-display-gst.c:443:21: warning: Value stored to 'duration' during its initialization is never read
- src/usb-backend.c:1507: large_shift: In expression "1 << address", left shifting by more than 31 bits has undefined behavior.
- src/spice-util.c:235: alloc_fn: Storage is returned from allocation function "whc_new".