fix(sync): extend wait time for RPC layer initialization (#13939)

When we start up DP, we need to make a meta call to CP first, so the first `do_sync` during the initial sync fails. It reports an ERR error: `rpc.lua:432: unable to create worker mutex and sync: rpc is not ready`. This experience is not ideal.

The initialization of the configuration also fails, and we have to wait for ourselves to wait 30 seconds (`sync_every(30s)`) before the configuration can sync successfully. This means that the DP will be unable to function for a period of time after connecting.

https://konghq.atlassian.net/browse/KAG-5922

kong/clustering/services/sync/rpc.lua

@@ -185,7 +185,9 @@ end
 
 -- check if rpc connection is ready
 local function is_rpc_ready()
-  for i = 1, 5 do
+  -- TODO: find a better way to detect when the RPC layer, including caps list,
+  --       has been fully initialized, instead of waiting for up to 5.5 seconds
+  for i = 1, 10 do
     local res = kong.rpc:get_peers()
 
     -- control_plane is ready