Add 'docker' to the list of known hypervisor types

nova-docker is out of tree, but it's starting to be used by people, and
being able to use a docker-specific hypervisor type can be quite useful
(in mixed-hypervisor environments, for instance).

Change-Id: I5a50de6bf73372f1ab999fd977aa58b33ffacfb9

nova/compute/hv_type.py

@@ -29,6 +29,7 @@ from nova import exception
 # even if not currently supported by OpenStack.
 BAREMETAL = "baremetal"
 BHYVE = "bhyve"
+DOCKER = "docker"
 FAKE = "fake"
 HYPERV = "hyperv"
 KQEMU = "kqemu"
@@ -48,6 +49,7 @@ ZVM = "zvm"
 ALL = (
     BAREMETAL,
     BHYVE,
+    DOCKER,
     FAKE,
     HYPERV,
     KQEMU,

nova/tests/unit/compute/test_hvtype.py

@@ -25,6 +25,9 @@ class HvTypeTest(test.NoDBTestCase):
     def test_valid_constant(self):
         self.assertTrue(hv_type.is_valid(hv_type.QEMU))
 
+    def test_valid_docker(self):
+        self.assertTrue(hv_type.is_valid("docker"))
+
     def test_valid_bogus(self):
         self.assertFalse(hv_type.is_valid("acmehypervisor"))