Getting LAN and WAN interfaces from UCI

[wwahammy]

Currently, we hard code the LAN and WAN interfaces either in openwrt_router.py or a subclass. While it's important to have defaults, we could just as easily get this information using uci show network.lan.interface and uci show network.wan.interface respectively. This would potentially be more flexible and reliable.

There are few unanswered questions about how this would function. These include:

• what happens if the network.lan.interface and network.wan.interface values change as part of a test?
• what happens if one of the interfaces is actually a bridge and has multiple interfaces listed in network.lan.interface? For example, if network.lan.interface='eth0.2 eth1', (real case for db120 default configuration in OpenWrt CC) what should we set as the lan interface for our test?