Add SQLServer XA DataSource class name

Closes gh-3604

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DatabaseDriver.java

@@ -86,7 +86,7 @@ enum DatabaseDriver {
 	/**
 	 * SQL Server
 	 */
-	SQLSERVER("com.microsoft.sqlserver.jdbc.SQLServerDriver");
+	SQLSERVER("com.microsoft.sqlserver.jdbc.SQLServerDriver", "com.microsoft.sqlserver.jdbc.SQLServerXADataSource");
 
 	private final String driverClassName;