clippy fix: calls to `drop` with a value that implements `Copy`

clippy fix: calls to `drop` with a value that implements `Copy`

Dropping a copy leaves the original intact

See:
https://rust-lang.github.io/rust-clippy/master/index.html#drop_copy

I assume the `drop` was used to silence a 'unused variable' warning,
so I silenced it by other means.

Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>