Disabling mdns in default config

[aphelionz]

CI issue, go-ipfs tests are failing.

socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 36
connect(36, {sa_family=AF_INET, sin_port=htons(33699), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation
 now in progress)
epoll_ctl(13, EPOLL_CTL_ADD, 36, {EPOLLOUT, {u32=36, u64=36}}) = 0
epoll_wait(13, [{EPOLLOUT, {u32=36, u64=36}}], 1024, 0) = 1
getsockopt(36, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
write(36, "POST /api/v0/pubsub/peers?arg=XX"..., 219) = 219
epoll_ctl(13, EPOLL_CTL_ADD, 36, {EPOLLIN, {u32=36, u64=36}}) = -1 EEXIST (File exists)
epoll_ctl(13, EPOLL_CTL_MOD, 36, {EPOLLIN, {u32=36, u64=36}}) = 0
epoll_wait(13, [], 1024, 0)             = 0
epoll_wait(13, [{EPOLLIN, {u32=36, u64=36}}], 1024, 199) = 1

Disabling this on a hunch worked in CI so now I'm trying and see if CircleCI doesn't clam up consistently.