client/tailscale, cmd/tailscale/cli: plumb --socket through

Without this, `tailscale status` ignores the --socket flag on macOS and
always talks to the IPNExtension, even if you wanted it to inspect a
userspace tailscaled.

Signed-off-by: David Crawshaw <crawshaw@tailscale.com>

cmd/tailscale/cli/cli.go

@@ -20,6 +20,7 @@ import (
 	"text/tabwriter"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/ipn"
 	"tailscale.com/paths"
 	"tailscale.com/safesocket"
@@ -88,6 +89,8 @@ change in the future.
 		return err
 	}
 
+	tailscale.TailscaledSocket = rootArgs.socket
+
 	err := rootCmd.Run(context.Background())
 	if err == flag.ErrHelp {
 		return nil