Add test case for showing host details

Tempest has provided test for listing volume hosts, but lacks test
for showing details of a volume host. This patch adds the support.

Including:
[1] Add show host API to volume v2 hosts_client library
[2] Add release note
[3] Add test case for showing volume host details
[4] Add unit tests for hosts_client API
[5] Fix for test_list_hosts

Change-Id: I72e91bb86fbc65083aceb59a59b0a375904c7678
diff --git a/releasenotes/notes/add-show-host-to-hosts-client-library-c60c4eb49d139480.yaml b/releasenotes/notes/add-show-host-to-hosts-client-library-c60c4eb49d139480.yaml
new file mode 100644
index 0000000..0de1803
--- /dev/null
+++ b/releasenotes/notes/add-show-host-to-hosts-client-library-c60c4eb49d139480.yaml
@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Add show host API to the volume v2 hosts_client library.
+    This feature enables the possibility to show details for a host.