After READONLY, a replicas behaves as its primary regarding returning
ASK redirects and TRYAGAIN.

Without this patch, a client reading from replicas cannot tell if a
key doesn't exist or if it's being migrated to another slot. Therefore,
without an ASK redirect in this situation, reading from replicas wasn't
reliable.

The target of a redirect is always a primary. If a client wants to
continue reading from a replica after following a redirect, it needs to
figure out the replicas of that primary using CLUSTER SHARDS or similar.

Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>