Add functional_creds.conf to .gitignore

This patch adds two files to .gitignore.
*  `functional_creds.conf` is used for functional test
* `functional-tests.log` is generated by functional test

Change-Id: Ie21e8e20078770746117a8976444d9a72fd45d55
Closes-Bug: #1508797

.gitignore

@@ -29,6 +29,10 @@ nosetests.xml
 .testrepository
 .venv
 
+# Functional test
+functional-tests.log
+functional_creds.conf
+
 # Translations
 *.mo