Adding description for testcases - compute part12

When Tempest is used in customer site, often we are required to
provide a testcase list including testcase names and descriptions.
Now no this kind of doc is available, so we can add descriptions
with the format of doc string for every testcase, so later we
can generata such a testcase description list.

There are hundreds of testcases missing descriptions, so we can
add them gradually, and limit the modified files in one patch
for the convenience of reviewing.

Change-Id: I5564ff0b71f56445977a79c2c813b2e3e31000c9
partially-implements: blueprint testcase-description
diff --git a/tempest/api/compute/servers/test_attach_interfaces.py b/tempest/api/compute/servers/test_attach_interfaces.py
index c1af6c7..0601bbe 100644
--- a/tempest/api/compute/servers/test_attach_interfaces.py
+++ b/tempest/api/compute/servers/test_attach_interfaces.py
@@ -99,6 +99,7 @@
 
 
 class AttachInterfacesTestJSON(AttachInterfacesTestBase):
+    """Test attaching interfaces"""
 
     def wait_for_port_detach(self, port_id):
         """Waits for the port's device_id to be unset.
@@ -230,6 +231,7 @@
     @decorators.idempotent_id('73fe8f02-590d-4bf1-b184-e9ca81065051')
     @utils.services('network')
     def test_create_list_show_delete_interfaces_by_network_port(self):
+        """Test create/list/show/delete interfaces by network port"""
         server, ifs, _ = self._create_server_get_interfaces()
         interface_count = len(ifs)
         self.assertGreater(interface_count, 0)
@@ -262,6 +264,7 @@
     @decorators.idempotent_id('d290c06c-f5b3-11e7-8ec8-002293781009')
     @utils.services('network')
     def test_create_list_show_delete_interfaces_by_fixed_ip(self):
+        """Test create/list/show/delete interfaces by fixed ip"""
         # NOTE(zhufl) By default only project that is admin or network owner
         # or project with role advsvc is authorised to create interfaces with
         # fixed-ip, so if we don't create network for each project, do not
@@ -290,7 +293,7 @@
 
     @decorators.idempotent_id('2f3a0127-95c7-4977-92d2-bc5aec602fb4')
     def test_reassign_port_between_servers(self):
-        """Tests the following:
+        """Tests reassigning port between servers
 
         1. Create a port in Neutron.
         2. Create two servers in Nova.
@@ -343,12 +346,15 @@
 
 
 class AttachInterfacesUnderV243Test(AttachInterfacesTestBase):
+    """Test attaching interfaces with compute microversion less than 2.44"""
+
     max_microversion = '2.43'
 
     @decorators.attr(type='smoke')
     @decorators.idempotent_id('c7e0e60b-ee45-43d0-abeb-8596fd42a2f9')
     @utils.services('network')
     def test_add_remove_fixed_ip(self):
+        """Test adding and removing fixed ip from server"""
         # NOTE(zhufl) By default only project that is admin or network owner
         # or project with role advsvc is authorised to add interfaces with
         # fixed-ip, so if we don't create network for each project, do not