cmd/tsidp: set hostinfo.App in tsnet mode (#16544)

This makes it easier to track how widely tsidp is used in practice.

Updates #cleanup

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

cmd/tsidp/tsidp.go

@@ -39,6 +39,7 @@ import (
 	"tailscale.com/client/local"
 	"tailscale.com/client/tailscale/apitype"
 	"tailscale.com/envknob"
+	"tailscale.com/hostinfo"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/tailcfg"
@@ -121,6 +122,7 @@ func main() {
 		}
 		defer cleanup()
 	} else {
+		hostinfo.SetApp("tsidp")
 		ts := &tsnet.Server{
 			Hostname: *flagHostname,
 			Dir:      *flagDir,