alfred: fix batadv-vis invocation in init.d script

broken (wouldn't start, failing silently) since commit:
 * "renamed vis to batadv-vis to avoid collisions with other vis binaries"

Signed-off-by: Gui Iribarren <gui@altermundi.net>
alfred: workaround race condition when batmanif is not ready at boot time

Wait up to 30 seconds during init.d script on boot, so that batmanif can
come up. If the timeout is reached, the init.d script refuses to start
alfred and related daemons.

This prevents an alfred crash when it would start during early boot, before
batmanif is available. Instead, alfred is started as soon as batmanif appears,
if that happens during the 30-second window.

Signed-off-by: Gui Iribarren <gui@altermundi.net>