tools/livepatch: Exit with 2 if a timeout occurs

tools/livepatch: Exit with 2 if a timeout occurs

Exit with 0 for success.
Exit with 1 for an error.
Exit with 2 if the operation should be retried for any reason (e.g. a
timeout or because another operation was in progress).

This allows a program or script driving xen-livepatch to determine if
the operation should be retried without parsing the output.

Acked-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>