using per-resource cache expiration_time fails

[Daniel Speichert]

clouds.yaml:

cache:
    class: dogpile.cache.dbm
    expiration_time: 3600
    arguments:
        filename: /tmp/os-shade-cache.dbm
    expiration:
        servers: 0
        flavors: 3600
        images: 3600
        networks: 3600
        floating_ips: 3600
        ports: 3600
        volumes: 3600

I identified two issues here:

1. Examples online say that under "expiraton", a singular form should be used ("server", "image"), yet shade is looking for plural, according to function names: https://github.com/openstack-infra/shade/blob/1d16f64fbf376a956cafed1b3edd8e51ccc16f2c/shade/openstackcloud.py#L249

2. The value in seconds is read from os_client_config as a string in
https://github.com/openstack-infra/shade/blob/1d16f64fbf376a956cafed1b3edd8e51ccc16f2c/shade/openstackcloud.py#L251

Therefore, this happens:

2017-10-26 16:48:39.501 41343 CRITICAL test [-] Unhandled error: dogpile.cache.exception.ValidationError: expiration_time is not a number or timedelta.
2017-10-26 16:48:39.501 41343 ERROR test Traceback (most recent call last):
2017-10-26 16:48:39.501 41343 ERROR test File "/root/venv/bin/sync", line 10, in <module>
2017-10-26 16:48:39.501 41343 ERROR test sys.exit(main())
2017-10-26 16:48:39.501 41343 ERROR test File "/root/test/main.py", line 34, in main
2017-10-26 16:48:39.501 41343 ERROR test cloud = shade.openstack_cloud(cloud=CONF.os_cloud, app_name=DOMAIN, region_name=CONF.os_region_name)
2017-10-26 16:48:39.501 41343 ERROR test File "/root/venv/lib/python3.6/site-packages/shade/__init__.py", line 113, in openstack_cloud
2017-10-26 16:48:39.501 41343 ERROR test return OpenStackCloud(cloud_config=cloud_config, strict=strict)
2017-10-26 16:48:39.501 41343 ERROR test File "/root/venv/lib/python3.6/site-packages/shade/openstackcloud.py", line 253, in __init__
2017-10-26 16:48:39.501 41343 ERROR test cache_class, expirations[expire_key], cache_arguments)
2017-10-26 16:48:39.501 41343 ERROR test File "/root/venv/lib/python3.6/site-packages/shade/openstackcloud.py", line 315, in _make_cache
2017-10-26 16:48:39.501 41343 ERROR test arguments=arguments)
2017-10-26 16:48:39.501 41343 ERROR test File "/root/venv/lib/python3.6/site-packages/dogpile/cache/region.py", line 435, in configure
2017-10-26 16:48:39.501 41343 ERROR test 'expiration_time is not a number or timedelta.')
2017-10-26 16:48:39.501 41343 ERROR test dogpile.cache.exception.ValidationError: expiration_time is not a number or timedelta.

Line 251 above simply needs to have: int(expirations[expire_key])