careful! these 2 commands will also remove the subdirectories themselves (you do not want that)
To clear cache & tmp you need to remove the contents from within these 2 dirs
rm -fr /var/lib/openhab2/cache/*
rm -fr /var/lib/openhab2/tmp/*
in general: be very careful with rm -rf 
Try to upgrade again to OH 2.3, get some logs and open up a new thread to troubleshoot it. For sure it will work !