qga-win: install service with --retry-path set by default

It's nicer from a management perspective that the agent can survive
hotplug/unplug of the channel device, or be started prior to the
installation of the channel device's driver without and still be able
to resume normal function afterward. On linux there are alternatives
like systemd to support this, but on w32 --retry-path is the only
option so it makes sense to set it by default when installed as a
w32 service.
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

qga/installer/qemu-ga.wxs

@@ -78,7 +78,7 @@
               Account="LocalSystem"
               ErrorControl="ignore"
               Interactive="no"
-              Arguments="-d"
+              Arguments="-d --retry-path"
               >
             </ServiceInstall>
             <ServiceControl Id="StartService" Start="install" Stop="both" Remove="uninstall" Name="QEMU-GA" Wait="no" />