Set default linktype LINUX_SLL2 when capturing on the "any" device

[tcpdump] / tests / aoe-oobr-1.out

    1  06:58:21.1048579 AoE length 18, Ver 1, Flags: [Response, MBZ-0x02, MBZ-0x01]
        Major: 0x40f6, Minor: 0x02, Command: Reserve/Release, Tag: 0x01010101
        RCmd: Set reserve list, NMacs: 1 [|aoe]