Code review comment for lp:~percona-toolkit-dev/percona-toolkit/fix-1062563-1063912-ptc-pxc-bugs

->start_sandbox, ->stop_sandbox and ->port_for are pseudo-vestigial (they are wrappers that aren't needed, but I find ->start_sandbox(master => "master3") simpler than `$trunk/sandbox/start-sandbox master 2900` -- mostly because I keep getting the port numbers numbers wrong).

set_as_slave and start_cluster are there mostly for convenience and brevity.

But since they are all ultimately wrappers around the sandbox/ scripts, sure, it could be done.