Maximum length for icon field causes tests to fail

[dmpiergiacomo]

Hi,

I believe that forwarding an icon of 128 bytes causes test_rk_maximum_list_capacity_per_rp_nodisplay and test_rk_maximum_size_nodisplay to fail against the Solo authenticator when PIN is provided.

I should investigate more, but from a quick look it seems like Solo sets the last usable byte of the icon field to 0. Should then the tests above forward an icon of 127 bytes instead, or should the Solo authenticator code be modified to return 128 bytes?

Notice that the current version of the Solo authenticator hits other errors before replicating the above. Consider this pull request to solve those errors and reproduce what has been written here above.