qga-win: Fixing msi upgrade disallow in WiX file

qga-win: Fixing msi upgrade disallow in WiX file

Issue: When upgrading qemu-ga using the msi from an old version
       to a newer one, the upgrade is not allowed by the msi
       showing this error message "Another version of this product
       is already installed."

BZ# 1536331: https://bugzilla.redhat.com/show_bug.cgi?id=1536331

Fix: For the upgrade to be allowed by the msi the WiX file must
     provide three things:
      1. Changing product's Id. (assigning it to "*")
      2. Constant product's UpgradeId. (exists)
      3. Changing version. (exists)

Reference: http://wixtoolset.org/documentation/manual/v3/howtos/updates/major_upgrade.html

Signed-off-by: Bishara AbuHattoum <bishara@daynix.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>