Revert "Initial changes to support SQL Server on Linux"

DBLIB is a poop drive with tons of bugs.
Based on other comments on GitHub, this driver will not be supported.

This reverts commit 42fae60958ec07062c3845d641f51e17ecae6a83.

Cake/Database/Driver/Sqlserver.php

@@ -61,17 +61,12 @@ class Sqlserver extends \Cake\Database\Driver {
 			$config['flags'][PDO::SQLSRV_ATTR_ENCODING] = $config['encoding'];
 		}
 		if (empty($config['dsn'])) {
-			if ($this->pdoDriverName() === 'sqlsrv') {
-				$config['dsn'] = "sqlsrv:Server={$config['host']};Database={$config['database']}";
-			} else {
-				$config['dsn'] = "dblib:host={$config['host']};dbname={$config['database']}";
-			}
+			$config['dsn'] = "sqlsrv:Server={$config['host']};Database={$config['database']}";
 		}
 
 		$this->_connect($config);
 
 		$connection = $this->connection();
-		$connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
 		if (!empty($config['init'])) {
 			foreach ((array)$config['init'] as $command) {
 				$connection->exec($command);
@@ -86,33 +81,13 @@ class Sqlserver extends \Cake\Database\Driver {
 	}
 
 /**
- * Establishes a connection to the databse server
- *
- * @param array $config configuration to be used for creating connection
- * @return boolean true on success
- */
-	protected function _connect(array $config) {
-		if ($this->pdoDriverName() !== 'sqlsrv') {
-			$connection = new PDO($config['dsn'], $config['login'], $config['password']);
-		} else {
-			$connection = new PDO($config['dsn'], $config['login'], $config['password'], $config['flags']);
-		}
-		$this->connection($connection);
-		return true;
-	}
-
-/**
  * Returns whether php is able to use this driver for connecting to database
  *
  * @return boolean true if it is valid to use this driver
  */
 
 	public function enabled() {
-		return in_array($this->pdoDriverName(), PDO::getAvailableDrivers());
-	}
-
-	protected function pdoDriverName() {
-		return strtoupper(substr(PHP_OS, 0, 3)) === 'WIN' ? 'sqlsrv' : 'dblib';
+		return in_array('sqlsrv', PDO::getAvailableDrivers());
 	}
 
 }