bugfix/incorrect-tos-representation

This patch causes OpenNaaS to use decimal format for ToS values.

Before this patch, hexadecimal values were used.

However, values where not represented nor sent to floodlight using the format expected by floodlight.
Floodlight accepts decimal values or hexadecimal ones preceded by "0x" prefix. OpenNaaS was using the result of Integer.toHexString(i), which is not using any prefix. e.g. 10 was represented as "a" and floodlight expected value is "0xa".

Instead of changing default hexadecimal representation, we changed to decimal one, which turned to be simpler.