tst_qlocalsocket: get rid of QtScript dependency

tst_qlocalsocket: get rid of QtScript dependency

Removing the lackey executable that needs QtScript to be built.
This was a qscript bastard that was able to run a client and a server
script. It's replaced by a C++ version with the same functionality.

Nice side effect: the two second wait per test row could be removed.
The client executable is now waiting for the server to be created.

Task-number: QTBUG-24142

Change-Id: I135b75abf6620d3b0af50dc226ea8c81c2bf4149
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>