Please try to get the local settings for the user openhab:
sudo su -s /bind/bash openhab
Should open a bash for user openhab, even if the bash is set to /bin/false.
Now take a look at locale
Another thing would be to take a look at /etc/default/locale,
this is mine:
# File generated by update-locale
LC_ALL=de_DE.UTF-8
LANG=de_DE.UTF-8
In fact, I did an edit on this file 
but openhab gives me german Weekdays all the time (now OH2.2 #1088)