keybase push of existing PGP key shouldn't make me@keybase.io primary

## Steps to Reproduce
- have an existing PGP key with an email (different than user@keybase.io), e.g. "user@example.dev"
- `keybase login`
- `keybase push`
- Choose _option (2)_, having keybase CLI add the email "keybase.io/user <user@keybase.io>"
- Observe that "user@example.dev" is no longer the primary email for the key; instead "user@keybase.io" is primary

Presumably `keybase push --add-email` has an equivalent result, but I didn't test that.
## Expected Behavior

The original primary email (user@example.dev) should remain as the primary email.

Start by reproducing the issue with an existing PGP key, then run `keybase push` and choose option (2) while recording the original primary email. Check the equivalent `keybase push --add-email` path if relevant. Done means adding the keybase.io email without changing the existing primary email.

Written by the indexing model from the issue text.