In Nova flavors it is ok to specify a decimal RXTX factor.
For this reason when applying QoS to a port Neutron should not
convert this factor to an integer value, but simply ensure
it's a valid float number and positive.
Cherry-picked from commit: 538a7bf3c7
Partial-Bug: #1463363
Change-Id: I983123ef7fd8f1b52b358aff3b579459fce63033