Fix unit test messing up the transaction on Oracle

Since the unit test is skipped anyway for Oracle, the dropTable() call
should be skipped as well to avoid having a leftover transaction and
cause further transactions to be nested and break the next test suites
requiring transactions.

tests/lib/db/mdb2schemamanager.php

@@ -12,6 +12,11 @@ namespace Test\DB;
 class MDB2SchemaManager extends \PHPUnit_Framework_TestCase {
 
 	public function tearDown() {
+		// do not drop the table for Oracle as it will create a bogus transaction
+		// that will break the following test suites requiring transactions
+		if (\OC::$server->getConfig()->getSystemValue('dbtype', 'sqlite') === 'oci') {
+			return;
+		}
 		\OC_DB::dropTable('table');
 	}