Support separate cache values for each tenant

[Kairat Kushaev]

Test case to reproduce:
0. create 2 tenants and users for them, configure memcache for heat.
1. create a flavor for tenant1
2. create a stack for tenant1 with server that refers to flavor from step 1
3. create a stack for tenant2 with server that refers to flavor from step 1 (but this flavor was not created for tenant2).
AR: validation passes
ER: validation should fail.
The reason is because current cache key doen't have tenant_id in it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/206006

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/206006
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=386bf2a6bccb682eca23fe0801fef87102d5d58d
Submitter: Jenkins
Branch: master

commit 386bf2a6bccb682eca23fe0801fef87102d5d58d
Author: kairat_kushaev <email address hidden>
Date: Mon Jul 27 13:49:28 2015 +0300

    Add tenant_id to heat cache key

    Currently heat caches validation results with the following key:
    <service name> + <value>.
    The patch changes this to
    <service name> + <tenant_id> + <value>.
    It allows names to be safely used and not be confused with
    values received from other tenants.

    Change-Id: Idd3fcf6afb3990be7df25fa1c5ef0c58222a5967
    Closes-bug: #1478525