Allow Keystoneclient 0.3.x

python-keystoneclient recently tagged 0.3.0, which
provides the v3 auth client. Raise upper bound to 0.4.
Also raise lower bound to 0.2.1, which is needed for
keystone (blueprint ec2signer-to-keystoneclient commit).

Change-Id: I8aef60612bc8c6972ec0aa833724d3382f909d97
Merge "Allow Keystoneclient 0.3.x"