core: add auto-startup parameters to engine-config

Add two parameters which are related to restart of highly-available VM
to engine-config:
1. For setting the maximum number of attempts that will be made in order
to restart highly-available VM that crashed
2. For setting the interval (in seconds) between those restart attempts

Change-Id: I9bf0953b5808020cbfa39a79385faf442b5e13a0
Signed-off-by: Arik Hadas <ahadas@redhat.com>