linux_udev: Log error code on pthread_create failure

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
hotplug: ensure udev monitor fd is non-blocking

Some older versions of udev do not automatically set the udev
monitor fd to non-blocking mode. This patch ensures that this is
always set.

HdG: Get flags then or in O_NONBLOCK and set them, rather then setting flags
to only O_NONBLOCK.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
libusb_get_bos_descriptor: Don't log an error on devices without a BOS

An error of LIBUSB_ERROR_PIPE simply means the device has no BOS, so don't
log an error to the console for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
linux_udev: Join the hotplug-event-thread when we stop event monitoring

To ensure that it is stopped before we continue (and if later libusb
gets re-initialized start another thread).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>