flatten the result structure

flat is better than nested

docs/frontends/webapi.rst

@@ -1861,13 +1861,11 @@ of the introducer(s) and storage server(s), here's an example::
    },
    "servers": [{
      "nodeid": "other_nodeid",
-     "description": {
      "available_space": 123456,
      "nickname": "George \u263b",
      "version": "1.0",
      "connection_status": "summary",
      "last_received_data": 1487811257
-     }
     }]
   }
 
@@ -1875,15 +1873,15 @@ of the introducer(s) and storage server(s), here's an example::
 The above json ``introducers`` section includes a list of
 introducer connectivity status messages.
 
-The above json ``servers`` section is a map
-where the key is a storage server node ID and the value
-is a map of properties with the following usage for each key:
+The above json ``servers`` section is an array with map elements.  Each map
+has the following properties:
 
-1. ``available_space`` - the available space in bytes expressed as an integer
-2. ``nickname`` - the storage server nickname
-3. ``version`` - the storage server Tahoe-LAFS version
-4. ``connection_status`` - connectivity status
-5. ``last_received_data`` - the time when data was last received,
+1. ``nodeid`` - an identifier derived from the node's public key
+2. ``available_space`` - the available space in bytes expressed as an integer
+3. ``nickname`` - the storage server nickname
+4. ``version`` - the storage server Tahoe-LAFS version
+5. ``connection_status`` - connectivity status
+6. ``last_received_data`` - the time when data was last received,
    expressed in seconds since epoch
 
 ``GET /status/``

src/allmydata/test/web/test_web.py

@@ -754,23 +754,19 @@ class Web(WebMixin, WebErrorMixin, testutil.StallMixin, testutil.ReallyEqualMixi
                 },
                 u'servers': sorted([
                     {u"nodeid": u'other_nodeid',
-                     u"description": {
                      u'available_space': 123456,
                      u'connection_status': u'summary',
                      u'last_received_data': None,
                      u'nickname': u'other_nickname \u263b',
                      u'version': u'1.0',
                     },
-                    },
                     {u"nodeid": u'disconnected_nodeid',
-                     u"description": {
                      u'available_space': 123456,
                      u'connection_status': u'summary',
                      u'last_received_data': None,
                      u'nickname': u'disconnected_nickname \u263b',
                      u'version': u'1.0',
                     },
-                    },
                 ]),
             }
             self.assertEqual(expected, decoded)

src/allmydata/web/root.py

@@ -214,10 +214,7 @@ class Root(MultiFormatPage):
 
     def _describe_known_servers(self, broker):
         return sorted(list(
-            {
-                u"nodeid": server.get_serverid(),
-                u"description": self._describe_server(server),
-            }
+            self._describe_server(server)
             for server
             in broker.get_known_servers()
         ))
@@ -225,6 +222,7 @@ class Root(MultiFormatPage):
 
     def _describe_server(self, server):
         description = {
+            u"nodeid": server.get_serverid(),
             u"connection_status": server.get_connection_status().summary,
             u"available_space": server.get_available_space(),
             u"nickname": server.get_nickname(),