wpctl: use auto cleanup for the `WpCtl` object
This is already done for `WpDaemon` and `WpExec`, so let's do it
here as well. This prevents some memory leaks in error paths,
which makes it easier to find real issues in the ASan output.
This is already done for `WpDaemon` and `WpExec`, so let's do it
here as well. This prevents some memory leaks in error paths,
which makes it easier to find real issues in the ASan output.