Revert NettyByteBuf.asReadOnly change (mongodb#1871)

Originally introduced in 057649f
This change had the unintended side effect of leaking netty ByteBufs when logging.

JAVA-5982

Author: rozza

driver-core/src/main/com/mongodb/internal/connection/netty/NettyByteBuf.java

@@ -251,7 +251,7 @@ public ByteBuf limit(final int newLimit) {
 
     @Override
     public ByteBuf asReadOnly() {
-        return new NettyByteBuf(proxied.asReadOnly().retain(), false);
+        return this;
     }
 
     @Override

driver-core/src/test/functional/com/mongodb/internal/connection/CommandHelperSpecification.groovy

@@ -25,6 +25,7 @@ import com.mongodb.connection.SocketSettings
 import com.mongodb.internal.connection.netty.NettyStreamFactory
 import org.bson.BsonDocument
 import org.bson.BsonInt32
+import spock.lang.Ignore
 import spock.lang.Specification
 
 import java.util.concurrent.CountDownLatch
@@ -52,9 +53,11 @@ class CommandHelperSpecification extends Specification {
     }
 
     def cleanup() {
+        InternalStreamConnection.setRecordEverything(false)
         connection?.close()
     }
 
+    @Ignore("JAVA-5982")
     def 'should execute command asynchronously'() {
         when:
         BsonDocument receivedDocument = null