Unable to update pubkey on website after signing

@siigna signed my key from Keybase and then sent it to me. I took the key and tried to update it using the website but it told me I couldn't have more than one primary key. It didn't have a place for me to select to just update it. I ran `keybase push newpubkey.key --update` and it accepted the update on the site. @siigna wiped his gpg data and started fresh and could then confirm my key had signatures.

The report concerns the website's key-update flow and the `keybase push newpubkey.key --update` workaround. Start by reproducing the update attempt with an already-signed key and compare it with the CLI path; done means the website accepts the update without rejecting it as a second primary key.

Written by the indexing model from the issue text.