[CP-4869] Check for WoW64 being turned off before installing 

This avoids an error case which has cropped up a few times in support calls and is which is difficult to track down the cause of, where things work unusually because WoW64 is redirecting system paths which (being designed for AnyCPU we don't expect)

Signed-off-by: Ben Chalmers <Ben.Chalmers@citrix.com>