absolute_path_not_starting_with_crate lint firing twice for the same import

[alexcrichton]

The absolute_path_not_starting_with_crate lint is firing twice for the same import (even after #50969) which cause rustfix to get confused and many warnings continue to get emitted:

#![crate_type = "rlib"]
#![allow(unused_imports, dead_code)]
#![feature(rust_2018_preview)]
#![warn(rust_2018_compatibility)]

mod foo {
    pub fn bar() {}
}

mod another {
    use foo::{self, bar};
}

$ rustc foo.rs
warning: absolute paths must start with `self`, `super`, `crate`, or an external crate name in the 2018 edition
  --> foo.rs:11:9
   |
11 |     use foo::{self, bar};
   |         ^^^^^^^^^^^^^^^^ help: use `crate`: `crate::foo::{self, bar}`
   |
note: lint level defined here
  --> foo.rs:4:9
   |
4  | #![warn(rust_2018_compatibility)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^
   = note: #[warn(absolute_path_not_starting_with_crate)] implied by #[warn(rust_2018_compatibility)]
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
   = note: for more information, see issue TBD

warning: absolute paths must start with `self`, `super`, `crate`, or an external crate name in the 2018 edition
  --> foo.rs:11:15
   |
11 |     use foo::{self, bar};
   |               ^^^^ help: use `crate`: `crate::self`
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
   = note: for more information, see issue TBD

[alexcrichton]

cc @nikomatsakis