add test for SELEventsCollector

[kmlebedev]

go test -v
=== RUN   TestCollectSELEventsCollector
--- PASS: TestCollectSELEventsCollector (0.00s)
PASS
ok      github.com/prometheus-community/ipmi_exporter   0.397s

[bitfehler]

Thank you for your PR. Is there a specific reason you are wanting to test this? I am somewhat hesitant, because this would be mocking input where can't make any assertions about its format anyways (because parts of it are vendor-specifc, so all bets are off). I could maybe see how this might be useful to collect weird edge cases observed in the wild. Is there where this was going? If so, I'd be curious to hear about those first.