[NRPA] Do not establish encryption when using NRPA

If we connect to a bonded device, we try to establish encryption. But if
we are using an NRPA, this will always fail and may lead to lost-bond.
So don't do it.

Test: manual
Bug: 192475649
Change-Id: I69941844aa9a2a3af59c0fd307e0de799f62afee