umdns: fails to compile with gcc10

[Nick]

If u try to compile umdns with gcc10 it will fail with:

> service.c:240:10: error: 'strcpy' offset 6 from the object at 'b' is
> out of the bounds of referenced subobject 'name' with type 'uint8_t[]'
> {aka 'unsigned char[]'} at offset 6 [-Werror=array-bounds]
More detailed error:
https://github.com/berlin-open-wireless-lab/DAWN/issues/109#issuecomment-657483908

Bests,
Nick