fix crash "IOError:No such file or directory:'/liveos/version'" when install

Sometimes ovirt-node install failed , when reboot it and reinstall, maybe there is no "/liveos/version" file.
Or for some reason sometimes this file can't be found.

Then the install UI will crashed for reason "IOError:No such file or directory:'/liveos/version'".It's not friendly for the user.

Change-Id: I56adc04e0153ea4122e28101d65783967ba27eb1
Signed-off-by: boh.ricky <boh.ricky@gmail.com>