Raise OpenStack dependency floors

The previous floors were circa-2018 and exposed Nova/Neutron API paths
(notably the add_floating_ip_to_server server action) that have been
removed from modern OpenStack. Bump to one major below the versions
exercised by CI:

  openstacksdk           >=0.12.0   ->  >=3.0.0
  python-novaclient      >=7.0.0    ->  >=17.0.0
  python-swiftclient     >=3.2.0    ->  >=4.0.0
  python-neutronclient   >=6.0.0    ->  >=11.0.0
  python-keystoneclient  >=3.13.0   ->  >=4.0.0

Upper caps unchanged.

setup.py

@@ -51,11 +51,16 @@ REQS_GCP = [
     'google-api-python-client>=2.0,<3.0.0'
 ]
 REQS_OPENSTACK = [
-    'openstacksdk>=0.12.0,<5.0.0',
-    'python-novaclient>=7.0.0,<20.0',
-    'python-swiftclient>=3.2.0,<5.0',
-    'python-neutronclient>=6.0.0,<13.0',
-    'python-keystoneclient>=3.13.0,<7.0'
+    # Minimums match SDK generation tested against the OpenStack
+    # provider fixes in cloudbridge/providers/openstack/. The previous
+    # floors were circa-2018 and exposed Nova/Neutron APIs (e.g. the
+    # add_floating_ip_to_server action) that are gone from any modern
+    # OpenStack deployment.
+    'openstacksdk>=3.0.0,<5.0.0',
+    'python-novaclient>=17.0.0,<20.0',
+    'python-swiftclient>=4.0.0,<5.0',
+    'python-neutronclient>=11.0.0,<13.0',
+    'python-keystoneclient>=4.0.0,<7.0'
 ]
 REQS_FULL = REQS_AWS + REQS_GCP + REQS_OPENSTACK + REQS_AZURE
 # httpretty is required with/for moto 1.0.0 or AWS tests fail