Remove key-ordering sensitivity in fixtures

Previously, the field order was effectively taken from the last record in the fixture, but the values were ordered according to the array_unique call above - primarily determined by the first record in the fixture.  If these two orders differed, values were added under the wrong keys.

lib/Cake/TestSuite/Fixture/CakeTestFixture.php

@@ -277,7 +277,6 @@ class CakeTestFixture {
 				$fields = array_unique($fields);
 				$default = array_fill_keys($fields, null);
 				foreach ($this->records as $record) {
-					$fields = array_keys($record);
 					$values[] = array_values(array_merge($default, $record));
 				}
 				$nested = $db->useNestedTransactions;