fix(force_waker_pipe): swap receiver and sender fd

[haraldh]

Sender and receiver fd where swapped resulting in:

❯ RUSTFLAGS="--cfg mio_unsupported_force_waker_pipe" cargo test --test events events_all --all-features
   Compiling mio v0.8.8 (/home/harald/git/mio)
    Finished test [unoptimized + debuginfo] target(s) in 0.35s
     Running tests/events.rs (target/debug/deps/events-c745c521d9f052e3)

running 1 test
test events_all ... FAILED

failures:

---- events_all stdout ----
thread 'events_all' panicked at 'unable to wake: Os { code: 9, kind: Uncategorized, message: "Bad file descriptor" }', tests/events.rs:30:18
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

failures:
    events_all

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 1 filtered out; finished in 0.00s

error: test failed, to rerun pass `--test events`

Fixed that and added a CI test.

[Thomasdezeeuw]

Thanks @haraldh