Privkey export fails when SIA coins active

[smk762]

To Reproduce

1. Login
2. activate SC and/or SCZEN
3. Go to settings > security
4. Attempt privkeys export
5. See error

Screenshots

Expected behavior
SIA privkey export is not supported by KDF, returning the following in postman

{
    "error": "rpc:198] RPC call failed: lp_coins:5920] SiaCoin::display_priv_key: Unsupported"
}

To avoid loss of access to other coin pks, it should be excluded from the request.

Found in
test-sia branch