If you unplug a QMI device, the /dev/cdc-wdmX device
disappears but uqmi will continue to poll it endlessly.
Then, when you plug it back, you have 2 uqmi processes,
and that's bad, because 2 processes talking QMI to the
same device [and the same time] doesn't seem to work well.
Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>