bttester: add key-size and authorization based l2cap conn reject

In tests that expect returning error in response for l2cap
connection request we use predefined PSMs. This commit adds
check for required keysize (which will always return error,
as connection is not secure and key size will always be 0)
instead of setting security level 4 (which would return
insufficient authentication, not insufficient key size).
It also adds suport for PSM used in insufficient authorization
tests - choosing this PSM will set flag that triggers error
on channel accept.

This affects tests L2CAP/LE/CFC/BV-[10-15]-C

Signed-off-by: Krzysztof Kopyściński <krzysztof.kopyscinski@codecoup.pl>