rpcperms+rpc: add ServerActive state and set it when server started

lnrpc/stateservice.swagger.json

@@ -96,9 +96,11 @@
         "LOCKED",
         "UNLOCKED",
         "RPC_ACTIVE",
+        "SERVER_ACTIVE",
         "WAITING_TO_START"
       ],
-      "default": "NON_EXISTING"
+      "default": "NON_EXISTING",
+      "description": " - SERVER_ACTIVE: SERVER_ACTIVE means that the lnd server is ready to accept calls."
     },
     "protobufAny": {
       "type": "object",