Fix non-repeatable tests: Ignore order of registry entries

[LukasHerwartz]

When running the tests, sometimes there is an error due to the assert taking list ordering into account:

1) test register_name/4 (Swarm.RegistryTests)
     test/registry_test.exs:15
     match (=) failed
     The following variables were pinned:
       pid2 = #PID<0.360.0>
       pid1 = #PID<0.359.0>
     code:  assert [entry(name: _, pid: ^pid2, ref: _, meta: _, clock: _), entry(name: _, pid: ^pid1, ref: _, meta: _, clock: _)] = Swarm.Registry.get_by_meta(:mfa, {MyApp.WorkerSup, :register, []})
     right: [
              {:entry, {:test, 1}, #PID<0.359.0>,
               #Reference<0.1496879406.3479437313.42553>,
               %{mfa: {MyApp.WorkerSup, :register, []}}, {1, 1}},
              {:entry, {:test, 2}, #PID<0.360.0>,
               #Reference<0.1496879406.3479437313.42556>,
               %{mfa: {MyApp.WorkerSup, :register, []}}, {1, 1}}
            ]
     stacktrace:
       test/registry_test.exs:49: (test)

Finished in 78.4 seconds
48 tests, 1 failure

Randomized with seed 773925

This code change fixes this behaviour:

$ mix test --seed 773925

Finished in 79.0 seconds
48 tests, 0 failures

Randomized with seed 773925