Fix crash on reload

If sway is reloaded using a bindsym which has multiple commands, it
failed to detect the reload command, didn't create a duplicate of the
binding and would crash because the reload command frees the bindings.

For example:

    mode system {
        bindsym r reload, mode default
    }

In this example, the binding->command is "reload, mode default".

Fixes #2545

sway/commands/bind.c

@@ -310,7 +310,7 @@ void seat_execute_command(struct sway_seat *seat, struct sway_binding *binding)
 	bool reload = false;
 	// if this is a reload command we need to make a duplicate of the
 	// binding since it will be gone after the reload has completed.
-	if (strcasecmp(binding->command, "reload") == 0) {
+	if (strncasecmp(binding->command, "reload", 6) == 0) {
 		reload = true;
 		binding_copy = sway_binding_dup(binding);
 		if (!binding_copy) {