contrib/freifunk-gwcheck: Fix multiple problems with the gwcheck script: Exit when already running, fix problem not being able to connect when there is no default gateway left in the main table, also add custom ip rules for wan gateways

git-svn-id: http://svn.luci.subsignal.org/luci/trunk@9624 ab181a69-ba2e-0410-a84d-ff88ab4c47bc