`control_brace_style` and `match_arm_blocks` incompatability

Coming from #3373.

There seems to be an issue which sometimes occurs whenever these two options are present at the same time in a rustfmt configuration:

control_brace_style = 'AlwaysNextLine'
match_arm_blocks = false

For example, take the following snippet from a cargo new main.rs file:

fn main() {
	let fooooooo = "100000000000000000000000";
	let _bar = match fooooooo {
		"100000000000000000000000" => fooooooo.len() == 1 && fooooooo.contains("222222222222222222"),
		_ => unreachable!("Should not happen"),
	};
}

Running cargo fmt on this code results in the following error:

error[internal]: left behind trailing whitespace
 --> /home/iron-e/Programming/ACTIVE/rustfmt-error-example/src/main.rs:6:6:1
  |
6 |
  | ^^^^^^^^
  |

warning: rustfmt has failed to format. See previous 1 errors.

It seems that line 4 of the snippet being >=95 characters long has something to do with it. The rest of the code is just filler to get it to compile.

Reproduce the issue using the provided main.rs snippet and the rustfmt configuration with control_brace_style = 'AlwaysNextLine' and match_arm_blocks = false; start by running cargo fmt. Compare behavior with shorter match-arm lines and identify the interaction that leaves trailing whitespace. Done means cargo fmt formats the example without the internal trailing-whitespace error.