backend: fail tests for bridges with invalid address
Depending on the type of bridge the address is used for the bridge connection or is a dummy address just as a placeholder. The rdsys now knows about what types use dummy addresses.
If the bridge uses the address and their address is invalid (a local network or other unrutable address) rdsys will not test those bridges and mark them as dysfunctional.
- Related: bridgestrap#40 (closed)