Replace API v1 with v1.1 in README
Replace API v1 with v1.1 in README

The current supported version is v1.1 and this change updates
the README file

Change-Id: Idd9b67f6348b661a1e4991891bf3c94236c7c6c5

openstack/zaqar,openstack/zaqar,openstack/zaqar,openstack/zaqar