Update AbstractClientHttpRequest with server changes

This commit updates `AbstractClientHttpRequest` to make it more similar
to its server counterpart.

spring-web/src/test/java/org/springframework/web/client/reactive/test/MockClientHttpRequest.java

@@ -92,13 +92,13 @@ public class MockClientHttpRequest extends AbstractClientHttpRequest {
 	@Override
 	public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
 		this.body = Flux.from(body);
-		return applyBeforeCommit().then(this.body.then());
+		return doCommit(() -> this.body.then());
 	}
 
 	@Override
 	public Mono<Void> writeAndFlushWith(Publisher<? extends Publisher<? extends DataBuffer>> body) {
 		this.bodyWithFlushes = Flux.from(body).map(p -> Flux.from(p));
-		return applyBeforeCommit().then(this.bodyWithFlushes.then());
+		return doCommit(() -> this.bodyWithFlushes.then());
 	}
 
 	public Publisher<DataBuffer> getBody() {
@@ -111,12 +111,12 @@ public class MockClientHttpRequest extends AbstractClientHttpRequest {
 
 	@Override
 	public Mono<Void> setComplete() {
-		return applyBeforeCommit().then();
+		return doCommit().then();
 	}
 
 	@Override
-	protected void writeHeaders() { }
+	protected void applyHeaders() { }
 
 	@Override
-	protected void writeCookies() { }
+	protected void applyCookies() { }
 }