Keypair tests failing on Fedora 22

[Artom Lifshitz]

To use an example, test_keypairs_post is failing on with:

NoMatch: Values do not match:
Template: ^([0-9a-f]{2}:){15}[0-9a-f]{2}$
Response: SHA256:4x+7c/6RKxVtSbQrFIRRH14GQzAgkRmbNd9QfsU/dXk

This happens on Fedora 22 because it introduced the following option to ssh-keygen:

     -E fingerprint_hash
             Specifies the hash algorithm used when displaying key fingerprints. Valid
             options are: “md5” and “sha256”. The default is “sha256”.

I'm guessing that the default used to be MD5 with no possibility to change it (which is what Nova expects), and now it's SHA256.

[Artom Lifshitz (notartom)]

This only affects stable/juno

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/juno
Review: https://review.openstack.org/189814