Confirm the presence of BT key when BT ON

After clearing Bluetooth data, the Bluetooth key will be cleared in the
same time. When turn on Bluetooth, NE happened at the step of checking
Bluetooth key.

Bug: 133214365
Test: ahost --host test net_test_bluetooth
Change-Id: I88f5dfae07352a794b304da60e09253c004fb3d4