Fix queue stats for v1.1 and above versions
Fix queue stats for v1.1 and above versions

Now in the cli of queue status v1, it's using queue.exists() to
check the existance. However, the queue.exists isn't supported
in v1.1 and above. But the queue stats should be support for
all the versions. As a result, user will see errors like
'Unavailable on versions >= 1.1'. This patches fixes it.

Closes-Bug: #1534427

Change-Id: Iaf738af4eca2419c6eba0a410b1f7e45c9720f54

openstack/python-zaqarclient