daemon-util: Fix quoting issue

This patch fixes a quoting issue in daemon-util:

$ EXTRA_MASTERD_ARGS=--no-voting /etc/init.d/ganeti restart
[…]
* ganeti-masterd...
/…/ganeti/daemon-util: line 65: local: `--no-voting': not a valid identifier

The reason was that the generated variables were not quoted properly and
the troublesome line expanded to
“local args=$MASTERD_ARGS $EXTRA_MASTERD_ARGS” instead of the correct
“local args="$MASTERD_ARGS $EXTRA_MASTERD_ARGS"”.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>