tools/pydfu.py: Call set_configuration() on fresh USB device object.
This call is required before using the device (some operating systems don't
need it but others do).  Fixes issue
@@ -81,6 +81,7 @@ def init():
if len(devices) > 1:
raise ValueError("Multiple DFU devices found")
__dev = devices[0]
+ __dev.set_configuration()
# Claim DFU interface
usb.util.claim_interface(__dev, __DFU_INTERFACE)
