Fix device-name when linking as secondary device

[gferon]

Also refactoredemptied a function that wasn't really useful, which will break compilation of downstream clients.

Resolves #121 and whisperfish/presage#38

Workaround before #124

[rubdos]

LGTM. The FIXME that you introduces should probably be tracked as an issue, I suppose.

[rubdos]

Should this become an issue?

[rubdos]

OK, I'll merge it now.

[rubdos]

error[E0061]: this function takes 3 arguments but 4 arguments were supplied
   --> libsignal-service-actix/examples/link.rs:54:27
    |
54  |         provision_manager.provision_secondary_device(
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected 3 arguments
55  |             &mut csprng,
    |             -----------
56  |             signaling_key,
    |             -------------
57  |             &args.device_name,
    |             -----------------
58  |             tx,
    |             -- supplied 4 arguments
    |
note: associated function defined here
   --> /home/rsmet/src/libsignal-service-rs/libsignal-service/src/provisioning/manager.rs:281:18
    |
281 |     pub async fn provision_secondary_device<R: rand::Rng + rand::CryptoRng>(
    |

Seems like we didn't check the examples :'-)

[gferon]

CI did fail though 😅 I'll fix it ASAP