create option to set ctl_dir for Net::OpenSSH

Net::OpenSSH is creating a control directory inside the user $HOME directory. But if the home directory doesn't have a chmod of 700 this will not work due to security concerns.

And sometimes it is also not possible to change the permissions of the home directory due to company policies.

So we need to have an option so that we can define the control directory.

Something like this (which would create the control directory inside the directory where the Rexfile is located):

ctl_dir "./.ctl";

Start by locating how Rex configures Net::OpenSSH and how options from the Rexfile are parsed, using the proposed ctl_dir "./.ctl" entry point. Trace the control-directory creation and determine how to make a configured directory work without relying on the user's HOME; done means the option is accepted and the control directory is created at the requested location.