logger: remove trailing spaces when outputing to journal

logger: remove trailing spaces when outputing to journal

Issues:
1. Whitespace-ish \r is not stripped, while it should be.
2. In journal \r is considered unprintable.

Lennart: "it is the duty of the client side to drop the trailing whitespace,
which "logger" doesn't do".

Reported-by: Ivan Babrou <ibobrik@gmail.com>
Explained-by: Lennart Poettering <lennart@poettering.net>
Reference: https://github.com/systemd/systemd/issues/3416
Signed-off-by: Sami Kerola <kerolasa@iki.fi>