Wrong param type in compute-service.rst

compute-service.rst file uses 'describe' for below
optional parameters

1. --long
2. --service <service>
3. --host <host>

This patchset changes type of these argument to option.

Change-Id: Ifd57bdf058efaeaa6cb43a7d4a60ee61ddb8de14
Closes-bug:#1563700

doc/source/command-objects/compute-service.rst

@@ -34,15 +34,15 @@ List service command
         [--long]
 
 .. _compute-service-list:
-.. describe:: --host <host>
+.. option:: --host <host>
 
-    Name of host
+    List services on specified host (name only) 
 
-.. describe:: --service <service>
+.. option:: --service <service>
 
-    Name of service
+    List only specified service (name only)
 
-.. describe:: --long
+.. option:: --long
 
     List additional fields in output
 

openstackclient/compute/v2/service.py

@@ -44,11 +44,11 @@ class ListService(command.Lister):
         parser.add_argument(
             "--host",
             metavar="<host>",
-            help="Name of host")
+            help="List services on specified host (name only)")
         parser.add_argument(
             "--service",
             metavar="<service>",
-            help="Name of service")
+            help="List only specified service (name only)")
         parser.add_argument(
             "--long",
             action="store_true",