net/interfaces: assume the network's up on js/wasm

Updates #3157

Change-Id: If4acd33598ad5e8ef7fb5960964c9ac32bc8f68b
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

net/interfaces/interfaces.go

@@ -414,6 +414,9 @@ func (s *State) HasPAC() bool { return s != nil && s.PAC != "" }
 
 // AnyInterfaceUp reports whether any interface seems like it has Internet access.
 func (s *State) AnyInterfaceUp() bool {
+	if runtime.GOOS == "js" {
+		return true
+	}
 	return s != nil && (s.HaveV4 || s.HaveV6)
 }