Dep's should be restricted by upper-constraints
Dep's should be restricted by upper-constraints

Tox trying to install latest versions for building docs which may
not be supported by stable and lower branches, so should be
restricted by respective version's upper-constraints.txt

Change-Id: I2cb297069e203bb6f4bc49576e86ae5e12cae33a

stackforge/ec2-api,openstack/ec2-api,stackforge/ec2-api,openstack/ec2-api