floss mgmt: Fix clippy warnings

- warning: this `MutexGuard` is held across an `await` point
- warning: you seem to be trying to use `match` for destructuring a
           single pattern. Consider using `if let`
- warning: methods with the following characteristics: (`to_*` and
           `self` type is `Copy`) usually take `self` by value
- warning: match expression looks like `matches!` macro
- warning: use of `format!` to build up a string from an iterator
- warning: in a `match` scrutinee, avoid complex blocks or closures with
           blocks; instead, move the block or closure higher and bind it
           with a `let`
- warning: you seem to want to iterate on a map's values

Bug: 343315863
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: ./build.py --target test
Flag: EXEMPT, Floss-only changes
Change-Id: Ief38ba9b870d952e52f8d8099c480c25bb03a67c