New flakey juju tests

[Martin Packman]

Another one from a recent change:

<http://juju-ci.vapour.ws:8080/job/github-merge-juju/12/console>

FAIL: networkinterfaces_test.go:72: NetworkInterfaceSuite.TestRemove
...
networkinterfaces_test.go:76:
    c.Assert(err, gc.ErrorMatches, `network interface .* not found`)
... error string = "" +
...     "network interface &{0xc210432b40 {S\xc0\bC\x9a\xc9\x05P\n" +
...     "\x00\x0eY aa:bb:cc:dd:ee:ff eth0 net1 0 true false}} not found"
... regex string = "network interface .* not found"
...
FAIL	github.com/juju/juju/state	89.308s

Added in pr 169:

<https://github.com/juju/juju/pull/169>

This looks pretty trivial, the error message has random binary junk in
it (bad) which happens to include a newline, which .* will not match.

Martin