Revert "Make ExecuteReaderAsync an async method."

This reverts commit 4169a0e.

Author: bgrainger

src/MySqlConnector/MySql.Data.MySqlClient/MySqlCommand.cs

@@ -261,13 +261,13 @@ protected override Task<DbDataReader> ExecuteDbDataReaderAsync(CommandBehavior b
 			return ExecuteReaderAsync(behavior, AsyncIOBehavior, cancellationToken);
 		}
 
-		internal async Task<DbDataReader> ExecuteReaderAsync(CommandBehavior behavior, IOBehavior ioBehavior, CancellationToken cancellationToken)
+		internal Task<DbDataReader> ExecuteReaderAsync(CommandBehavior behavior, IOBehavior ioBehavior, CancellationToken cancellationToken)
 		{
 			if (!IsValid(out var exception))
-				throw exception;
+				return Utility.TaskFromException<DbDataReader>(exception);
 
 			m_commandBehavior = behavior;
-			return await CommandExecutor.ExecuteReaderAsync(new IMySqlCommand[] { this }, SingleCommandPayloadCreator.Instance, behavior, ioBehavior, cancellationToken).ConfigureAwait(false);
+			return CommandExecutor.ExecuteReaderAsync(new IMySqlCommand[] { this }, SingleCommandPayloadCreator.Instance, behavior, ioBehavior, cancellationToken);
 		}
 
 		public MySqlCommand Clone() => new MySqlCommand(this);