Sometimes nepomuks owns a process on a mounted device. It is then impossible to umount the device without killing the nepomukservice

Reproducible: Sometimes

Steps to Reproduce:
1. mount SD card, USB stick, whatever with plasma's device notifier 
2. do some work on this device. Copy files over, rename sth and so on
3. umount via plasma's device notifier
Actual Results:  
"Could not unmount the following device: Kingston. One or more files on this device are still open within an application."

Expected Results:  
unmount the device.

$ lsof /dev/mmcblk0p1 
COMMAND   PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
nepomukse 867 roland   20r   DIR  179,1    32768    1 /run/media/roland/Kingston

$ ps aux | grep 867
roland     867  0.2  0.3 449392 27740 ?        SNl  10:34   0:02 /usr/bin/nepomukservicestub nepomukfilewatch