e key unauthenticated for high security

High security level for pre v2.1 devices requires combination link key
authenticated by at least 16 digit PIN code.

It's also necessary to update key_type and pin_length when the key
exists and is sufficently secured for the connection as there will be
no link key notify event in that case.

Signed-off-by: Waldemar Rymarkiewicz <waldemar.rymarkiewicz@tieto.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
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