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 set
timeout to '-1' if GRUB_RECORDFAIL_TIMEOUT not set. GRUB will wait use
choose bootable OS if timeout is '-1'. Now set GRUB_RECORDFAIL_TIMEOUT
and update grub before finished install to fix this issue.

Signed-off-by: Xu Tian <xutian@redhat.com>