Fix an unbalanced release of the producer's pending semaphore (#392)

### Motivation

Current code releases the producer's pending semaphore twice when batch is off and message is too big. The unbalanced release overflows the semaphore, and subsequent sends will fail with ProducerQueueIsFull.

### Modifications

Remove the redundant semaphore release as the necessary release will be done in `handleFailedResult`.

Author: erobot

lib/ProducerImpl.cc

@@ -630,7 +630,6 @@ void ProducerImpl::sendAsyncWithStatsUpdate(const Message& msg, SendCallback&& c
                 const uint32_t msgHeadersAndPayloadSize = msgMetadataSize + payloadSize;
                 if (msgHeadersAndPayloadSize > maxMessageSize) {
                     lock.unlock();
-                    releaseSemaphoreForSendOp(*op);
                     LOG_WARN(getName()
                              << " - compressed Message size " << msgHeadersAndPayloadSize << " cannot exceed "
                              << maxMessageSize << " bytes unless chunking is enabled");

tests/ProducerTest.cc

@@ -243,6 +243,8 @@ TEST_P(ProducerTest, testMaxMessageSize) {
     ASSERT_EQ(ResultMessageTooBig,
               producer.send(MessageBuilder().setContent(std::string(maxMessageSize, 'b')).build()));
 
+    ASSERT_EQ(ResultOk, producer.send(MessageBuilder().setContent(msg).build()));
+
     client.close();
 }