Await `ReadyForQuery` before emitting errors from transactional control methods

[mp911de]

Bug Report

commitTransaction() emits an error signal upon processing ErrorResponse. A subsequent call to rollbackTransaction fails with "no transaction in progress" because the driver hasn't processed the final ReadyForQuery frame.

The driver should await the entire completion before throwing the error signal.

Reproducer

Input Code

CREATE TABLE tst(x int CONSTRAINT test_me UNIQUE DEFERRABLE INITIALLY DEFERRED);

Steps to reproduce

Input Code

ConnectionFactory connectionFactory = ConnectionFactories.get("r2dbc:postgresql://postgres:postgres@localhost/postgres");

Connection block = Mono.from(connectionFactory.create()).block();

Mono.from(block.beginTransaction()).block();

Flux.from(block.createStatement("insert into tst values(1)").execute())
		.flatMap(it -> it.getRowsUpdated()).blockLast();

Flux.from(block.createStatement("insert into tst values(1)").execute())
		.flatMap(it -> it.getRowsUpdated()).blockLast();

Mono.from(block.commitTransaction()).block();