Suppress fiano warning

[xaionaro]

Fiano prints logs and this is non-disablable. See https://github.com/linuxboot/fiano/issues/330

In this PR I temporary suppress fiano-related logs when we call tools.GetRegion.

log.SetOutput uses a mutex, so it should be safe:

// SetOutput sets the output destination for the standard logger.
func SetOutput(w io.Writer) {
    std.mu.Lock()
    defer std.mu.Unlock()
    std.out = w
}

[xaionaro]

A better fix: https://github.com/linuxboot/fiano/pull/331