lime-system: activate mesh_nolearn if batman-adv is used

[a-gave]

I stumbled upon this while trying to find/produce a current list of wireless drivers that support ‘auto’ as a distance value (#1231)

Related links:

1. from Linux https://github.com/torvalds/linux/blob/7d0a66e4bb9081d75c82ec4957c50034cb0ea449/include/uapi/linux/nl80211.h#L5017-L5021

 * @NL80211_MESHCONF_NOLEARN: Try to avoid multi-hop path discovery (e.g.
 *      PREQ/PREP for HWMP) if the destination is a direct neighbor. Note that
 *      this might not be the optimal decision as a multi-hop route might be
 *      better. So if using this setting you will likely also want to disable
 *      dot11MeshForwarding and use another mesh routing protocol on top.

2. introduced in iw https://git.kernel.org/pub/scm/linux/kernel/git/jberg/iw.git/commit/?id=94ded888ba696a1ec03571d596e96cf944ccc0c8
3. from the commit message in the addition in Gluon freifunk-gluon/gluon@768172c (see also gluon-core: activate mesh_nolearn freifunk-gluon/gluon#3512 (comment))

We do not use the multi-hop mesh routing capabilities of 802.11s and
set mesh_fwding=0 in gluon unconditionally.
In turn there is no use in discovering 802.11s mesh paths,
as there are no multi-hop mesh paths due to the lack of forwarding.

While the router identifies this on its own after a few ms,
it is simply not necessary to waste resources on this discovery.