floss: Add a sysprop bluetooth.btm.sec.delay_auth_ms.value to floss

Floss is suffering from authentication racing between host and device.
Introduce the host delay to allow peripheral initiated authentication
to finish.

Bug: 301563951
Tag: #floss
Test: mma -j32
Test: emerge-brya floss
Change-Id: I8ffaaf001c8d6e81764ab4cf9e95558ea85f364a