Add accounts.yaml to .gitignore

This commit adds accounts.yaml to .gitignore. We don't need to track a
user specific file.

Change-Id: Id9c053bcd4bde3627506ee60853d11669ffcda34
diff --git a/.gitignore b/.gitignore
index 9292dbb..287db4c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 ChangeLog
 *.pyc
 __pycache__/
+etc/accounts.yaml
 etc/tempest.conf
 etc/tempest.conf.sample
 etc/logging.conf