ipn/ipnlocal: set the push device token correctly

It would end up resetting whatever hostinfo we had constructed
and leave the backend statemachine in a broken state.
This fixes that by storing the PushDeviceToken on the LocalBackend
and populating it on Hostinfo before passing it to controlclient.

Updates tailscale/corp#8940
Updates tailscale/corp#15367

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/localapi/localapi.go

@@ -1553,8 +1553,7 @@ func (h *Handler) serveSetPushDeviceToken(w http.ResponseWriter, r *http.Request
 		http.Error(w, "invalid JSON body", http.StatusBadRequest)
 		return
 	}
-	hostinfo.SetPushDeviceToken(params.PushDeviceToken)
-	h.b.ResendHostinfoIfNeeded()
+	h.b.SetPushDeviceToken(params.PushDeviceToken)
 	w.WriteHeader(http.StatusOK)
 }
 

ipn/localapi/localapi_test.go

@@ -15,7 +15,6 @@ import (
 	"testing"
 
 	"tailscale.com/client/tailscale/apitype"
-	"tailscale.com/hostinfo"
 	"tailscale.com/ipn/ipnlocal"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstest"
@@ -77,7 +76,7 @@ func TestSetPushDeviceToken(t *testing.T) {
 	if res.StatusCode != 200 {
 		t.Errorf("res.StatusCode=%d, want 200. body: %s", res.StatusCode, body)
 	}
-	if got := hostinfo.New().PushDeviceToken; got != want {
+	if got := h.b.GetPushDeviceToken(); got != want {
 		t.Errorf("hostinfo.PushDeviceToken=%q, want %q", got, want)
 	}
 }