Stop running siblings jobs and pin SDK

The OpenStackSDK project is in the process of making a breaking
API change and has stopped running this job on master.  Without
an interest in adjusting Nodepool to match before the release,
it is no longer useful to run this job on this repo.  Stop running
it until the sdk project is ready to re-establish co-gating.

We also set a constraint to avoid installing SDK 1.0.0 since we
expect that to include the breaking API change.

Change-Id: If9f45e24a71f349a85e94150e6a4d9ee9672173b

.zuul.yaml

@@ -286,7 +286,6 @@
       jobs:
         - opendev-buildset-registry
         - nodepool-build-image
-        - nodepool-build-image-siblings
         - zuul-tox-docs
         - tox-pep8
         - nodepool-tox-py36
@@ -295,7 +294,6 @@
         - nodepool-zuul-functional:
             voting: false
         - nodepool-functional-container-openstack-release
-        - nodepool-functional-container-openstack-siblings
         - nodepool-functional-k8s
         - nodepool-functional-openshift
         - zuul-quick-start:

requirements.txt

@@ -9,7 +9,8 @@ PrettyTable>=0.6,<0.8
 # openstacksdk before 0.27.0 is TaskManager based
 # 0.28.0-0.31.0 fail to upload images with glance tasks.
 # 0.31.1 and 0.31.2 have a bug with image deletion in tasks API
-openstacksdk>=0.27.0,!=0.28.0,!=0.29.0,!=0.30.0,!=0.31.0,!=0.31.1,!=0.31.2
+# We expect 1.0.0 to break the API we use
+openstacksdk>=0.27.0,!=0.28.0,!=0.29.0,!=0.30.0,!=0.31.0,!=0.31.1,!=0.31.2,<1.0.0
 diskimage-builder>=3.16.0
 voluptuous
 kazoo>=2.8.0