Mark LDAP password and admin_token secret

Add secret=True to LDAP password and admin_token
of keystone configuration.

Fix bug #1172195

Change-Id: I8ef7f705e3f6b374ff427c20eb761892d5146a75
(cherry picked from commit d43e2a51a1ed7adbed3c5ddf001d46bc4a824ae8)
Merge "Mark LDAP password and admin_token secret" into stable/grizzly