Fixes create flavor extras success_url

Change success_url "http://${ip}/admin/flavors/1/extras/" to
"http://${ip}/${LOGIN_REDIRECT_URL}/admin/flavors/1/extras/"

Closes-Bug:#1268860

Change-Id: I874d0e3a4c065097cfb4ed7572ac5df335b1ed96
Merge "Fixes create flavor extras success_url"