floss: SetName: Don't set the property if unchanged

This shall decrease the rate that SaveImmediately is called on shutting
down, avoid crashing when the disk is busy.

Bug: 310147428
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: Toggle BT fast, SaveImmediately is not called
Flag: EXEMPT, Floss-only changes
Change-Id: I2f132c586ccc9df839251be11c462a25e187d111