Floss: connect to LE identity addr if current random is unavailable

When restarting adapter, the current random address is uninitialized
making it's impossible to reconnect to LE device with Floss.
Use the current random address only if it's available.

Bug: 284012338
Test: Do the following steps.
      (1) Pair an LE device with IRK (e.g. MX Master 2S mouse)
      (2) Power off BT, power back on
      (3) Verify peer reconnects
Change-Id: Icf9a89783f26d00590b3c745af9857179204fd0a