[chore] compiling with rustc 1.35.0 warns on borrowing *self as mutable

[ghost]

Thank you for building and publishing this tool! I am trying it out to replace another process manager. I wanted to report this maintenance task for any contributor or user who may see this.
I cloned the repository as of c590366 and ran cargo build --release. It printed the following (and a few similar compiler warnings):

warning: cannot borrow `*self` as mutable because it is also borrowed as immutable
   --> src/main.rs:358:37
    |
357 |       match self.spec.procs[idx].shutdown {
    |             --------------- immutable borrow occurs here
358 |         Some(ref shutdown) => match self.run_command(&shutdown.clone(), &env, deadline, None) {
    |                                     ^^^^              -------- immutable borrow later used here
    |                                     |
    |                                     mutable borrow occurs here
    |
    = note: #[warn(mutable_borrow_reservation_conflict)] on by default
    = warning: this borrowing pattern was not meant to be accepted, and may become a hard error in the future
    = note: for more information, see issue #59159 <https://github.com/rust-lang/rust/issues/59159>

The upstream issue is rust-lang/rust#59159.

[andrewchambers]

Thank you for reporting this, this indeed needs to be fixed. I will look at it soon.

[andrewchambers]

Should be fixed now.