fix: Xen Version checks

[GabrielBuica]

I missed a few cases...

[lindig]

I wonder if parsing this using sscanf with a couple of expected formats would be better. Here is a similar tactic that I used in C code to parse hours:minutes:seconds:

static float hms_to_sec(const char *duration)
{
    int hours = 0, minutes = 0;
    float seconds = 0.0;
    int items;

    items = sscanf(duration, "%u:%u:%f", &hours, &minutes, &seconds);
    if (items == 3) {
        return (float) hours *3600.0 + (float) minutes *60.0 + seconds;
    }
    items = sscanf(duration, "%u:%f", &minutes, &seconds);
    if (items == 2) {
        return (float) minutes *60.0 + seconds;
    }
    items = sscanf(duration, "%f", &seconds);
    if (items == 1) {
        return seconds;
    }
    return -1.0;
}