sd-bus: escape invalid characters in error message

sd-bus: escape invalid characters in error message

At many places, we pass arguments of dbus method calls to
sd_bus_error_setf(), and produces unprintable log messages.
Let's always escape the generated error message.

This fixes something like the following:
```
[ 1921.875668] systemd-logind[611]: Got message type=method_call sender=:1.46 destination=:1.6 path=/org/freedesktop/login1 interface=org.freedesktop.login1.Manager member=GetSeat  cookie=1344 reply_cookie=0 signature=s error-name=n/a error-message=n/a
[ 1921.875758] systemd-logind[611]: [725B blob data]
[ 1921.875777] systemd-logind[611]: [768B blob data]
```