If the macnocker client tries to send data, but the interface is not running,
this will result in error messages. However, an interface being down is a
valid state and should not result in error messages. So first check the current
state of the interface before trying to send data.
Fixes: #104
Signed-off-by: Fabian Bläse <fabian@blaese.de>
Acked-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>