floss: Don't bookmark connectable mode if set mode failed

Set mode may fail in some cases such as the LibBluetooth stack is not
yet ready. In any case we just shouldn't save the new mode on failure.

Bug: 336881286
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: Stress run bluetooth_AdapterSRHealth.sr_while_powered_off.floss
Flag: EXEMPT, Floss-only changes
Change-Id: Ibb73f15cdb10cb8267fa28a444a205a589cd1544