Fix NetworkInterfaceSuite.TestRemove random failure
Merge pull request #298 from bz2/network_interface_random_test_failure

Fix NetworkInterfaceSuite.TestRemove random failure

The NetworkInterface type must be serialised as %#v not %v for errors.NotFoundf so the GoString method gets used. Also improve the test error match to ensure the correct serialisation is used. Without this change, the test could randomly fail if the bson id happened to contain an 0x0A byte, as `.*` does not match newlines.