build: Address issues found by 1.43.0 clippy

These are mostly due to use of "bare use" statements and unnecessary vector
creation.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vhost_user_fs/src/filesystem.rs

@@ -9,8 +9,6 @@ use std::io;
 use std::mem;
 use std::time::Duration;
 
-use libc;
-
 use crate::fuse;
 
 use super::fs_cache_req_handler::FsCacheReqHandler;