Providing -decoy option ends up sending a -1 generation number

[ewust]

If the user specifies the -decoy option (e.g. ./cli -connect-addr=1.2.3.4:443 -decoy colorado.edu,128.138.129.98), then the registration that gets sent will not send the generation ID from the ClientConf, and the station will get a MAX_UINT generation ID.

While the documentation warns that -decoy will ignore the ClientConf, it's still getting a public key from it. Ideally, we should:

1. add a -generation option to the CLI that overrides the ClientConf if it is provided
2. use the ClientConf generation if the above option is not provided
3. Error if none of the above are present