according to Horizon team's advice.
I've changed installation procedure as follows.
(before changing)
1. copy heat_policy.json from Heat-Dashboard directory
to Horizon directory (same as enable files)
2. add orchestration key to POLICY_FILES settings
(after changing)
1. just point Heat-Dashboard policy file path
from POLICY_FILES settings
Change-Id: Idaf2cbfcb716a9aa4c0f43283526302f062ea0a7
aea63e9826