openvpnmsica: properly schedule reboot in the end of installation

openvpnmsica: properly schedule reboot in the end of installation

A deferred custom action can not set the reboot status via MsiSetMode.

To schedule reboot:

 - get user's temp directory in immediate custom action
   (EvaluateTUNTAPAdapters) which is called in the beginning of
   installation and pass it to the deffered action

 - in deferred action (ProcessDeferredAction) create a special empty file
   in user's temp directory if reboot is required

 - in the end of installation call immediate custom action
   (CheckAndScheduleReboot) which checks the existence of special file
   and uses MsiSetMode() to schedule reboot

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20210511075739.158-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22335.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 2f0e3fe1c6c57dd3989951d167e94fe4debe5405)