memoized_with_request should return hashable types

[Yves-Gwenael Bourhis]

memoized_with_request functions should return hashable types, otherwise memoizing will not work
 because memoizing is based on the fact that function call arguments are hashable.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/334499

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/334499
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=eb3180f82710956713e659c73216012d558836b0
Submitter: Jenkins
Branch: master

commit eb3180f82710956713e659c73216012d558836b0
Author: Yves-Gwenael Bourhis <email address hidden>
Date: Mon Jun 27 15:55:05 2016 +0200

    Returning a tuple instead of list in list_extensions

    extension_supported is decorated with
    memoized_with_request(list_extensions, 1).
    This means that list_extensions is called to build the args for
    extension_supported and then make a hash.
    list_extensions was returning a list which is unhashable.
    We now return a tuple which has the following advantages:
    1: is hashable.
    2: tuples use less memory than lists in python, and should be use when we do
    not need a mutable.

    Change-Id: I92be6ef7880c6ac76847ec9cc8b2c83a6fd009b2
    Closes-Bug: #1596545

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/horizon 10.0.0.0b2 development milestone.