iso streaming: Add default port for all protocols

Kimchi supports iso streaming through the protocols: http, https,
ftp, ftps and tftp. So we need to be able to get the default
port for all those.

Signed-off-by: Aline Manera <alinefm@br.ibm.com>
bug fix: correct to use float when calculate guest net and disk IO

In [0]: float(1023) / 1024
Out[0]: 0.9990234375

In [1]: float(1023 / 1024)
Out[1]: 0.0

This patch corrects float usage for more precision result.
And also removes redundant float.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>