Make docstring of servers consistent

Docstring of service clients is very inconsistent, but we have a
plan to use it for generating API doc.
This patch makes docstring of servers consistent for fitting to
http://developer.openstack.org/api-ref-compute-v2.1.html
as a first step.

Change-Id: Icb51c2cf189fc17a91dcac5b95dc4a27afeac543
diff --git a/tempest/services/compute/json/servers_client.py b/tempest/services/compute/json/servers_client.py
index 1d2c7b2..e54cfe4 100644
--- a/tempest/services/compute/json/servers_client.py
+++ b/tempest/services/compute/json/servers_client.py
@@ -32,8 +32,8 @@
         self.enable_instance_password = enable_instance_password
 
     def create_server(self, **kwargs):
-        """
-        Creates an instance of a server.
+        """Create server
+
         Most parameters except the following are passed to the API without
         any changes.
         :param disk_config: The name is changed to OS-DCF:diskConfig
@@ -69,7 +69,8 @@
         return service_client.ResponseBody(resp, body)
 
     def update_server(self, server_id, **kwargs):
-        """Updates the properties of an existing server.
+        """Update server
+
         Most parameters except the following are passed to the API without
         any changes.
         :param disk_config: The name is changed to OS-DCF:diskConfig
@@ -84,20 +85,20 @@
         return service_client.ResponseBody(resp, body)
 
     def show_server(self, server_id):
-        """Returns the details of an existing server."""
+        """Get server details"""
         resp, body = self.get("servers/%s" % server_id)
         body = json.loads(body)
         self.validate_response(schema.get_server, resp, body)
         return service_client.ResponseBody(resp, body)
 
     def delete_server(self, server_id):
-        """Deletes the given server."""
+        """Delete server"""
         resp, body = self.delete("servers/%s" % server_id)
         self.validate_response(schema.delete_server, resp, body)
         return service_client.ResponseBody(resp, body)
 
     def list_servers(self, detail=False, **params):
-        """Lists all servers for a user."""
+        """List servers"""
 
         url = 'servers'
         _schema = schema.list_servers