Broke with d3c05574


Remove the logic for setting jom as default or not, and just set it as
default, since the new AbstractMsvcToolChain::makeCommand uses nmake as
a fallback if jom is not found.

Task-number: QTCREATORBUG-7876
Change-Id: Ia96c2449863fbbd027fbaf003d75bb6155206289
Reviewed-by: Oliver Wolff <oliver.wolff@nokia.com>