This commit adds a "truncate" flag that can be added to a service
description between the "tty" keyword and the path string.
If the flag is set, the output file is truncated to 0 after opening.
This probably requires some remodeling in the future as the tty keyword
no longer deals with just tty devices.
Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
