shared.unattended: fix ubuntu timeout lost issue

In system_set_bootable test, recordfail set to 1 when reset guest
before guest boot into OS, and make_timeout function in /etc/grub.d/00_header
will set timeout to -1 if GRUB_RECORDFAIL_TIMEOUT not set./ it will
block guest boot in to OS automaticly. Now set GRUB_RECORDFAIL_TIMEOUT
and update grub before finished install to fix this issue.

Signed-off-by: Xu Tian <xutian@redhat.com>