Fix clippy warnings

[russcam]

This commit fixes the clippy warnings around single_component_path_imports

[russcam]

clippy check github action is failing with

Checking api_generator v7.6.0-alpha.1 (/home/runner/work/elasticsearch-rs/elasticsearch-rs/api_generator)
  {"reason":"compiler-message","package_id":"elasticsearch 7.6.0-alpha.1 (path+file:///home/runner/work/elasticsearch-rs/elasticsearch-rs/elasticsearch)","target":{"kind":["lib"],"crate_types":["lib"],"name":"elasticsearch","src_path":"/home/runner/work/elasticsearch-rs/elasticsearch-rs/elasticsearch/src/lib.rs","edition":"2018","doctest":true},"message":{"rendered":"error: internal compiler error: src/librustc_mir/dataflow/generic/engine.rs:315: Switch on discriminant of non-ADT\n\n","children":[],"code":null,"level":"error: internal compiler error","message":"src/librustc_mir/dataflow/generic/engine.rs:315: Switch on discriminant of non-ADT","spans":[]}}
  thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:881:9
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
  
  note: the compiler unexpectedly panicked. this is a bug.
  
  note: we would appreciate a bug report: https://github.com/rust-lang/rust-clippy/issues/new
  
  note: Clippy version: clippy 0.0.212 (fc5d0cc 2020-02-24)

looking into

[russcam]

can reproduce issue locally. Opened rust-lang/rust-clippy#5238