send bcc-self even if delete from server is set to "at once"

[adbenitez]

if a big message is sent but waiting for the "OK sent" reply timeouts, now core detects the incoming message received via copy to self, and doesn't keep trying to send the message, however, if "delete messages from server" is set to "at once", the copy to self is not sent (that is, the message is sent as if "send copy to self" option is disabled)

it is better if the copy to self is sent, and then deleted "at once" this would give a chance to core to detect that a big attachment was sent and cancel retrying, specially this is the case for nauta.cu where "delete messages from server" is set to "at once" by default, see: deltachat/provider-db#272

[link2xt]

Made a fix: #5190