Only try to manage redirected registry keys/values on x64 systems

Previously, the acceptance test was trying to manage redirected keys and
values on x86 and x64 systems. However, on x86 systems, both 32:HKLM and
HKLM refer to the same key. As a result, only one 'created' message was
output for each pair of key/values, causing the acceptance test to fail.

This commit ensures we only test the redirected keys/values, those
prefixed with '32:' when run on x64 systems.
Detect whether sysnative filesystem alias is available

Previously the test assumed that the sysnative filesystem alias was
available, so that we could run the 64-bit version of reg.exe. However,
this fails when running on x86 versions of Windows. It also fails when
running on x64 on 2003, as the sysnative alias is not available until
Vista and later.

This commit logs a warning if the sysnative alias is not available on
x64 systems. Otherwise, it uses the 'native' version of reg.exe to
check for the default registry value.