record-tester: Fix stream health always firing with other errs

We were passing an always not nil error to sendPagerDutyEvent.

We could make the error a pointer, but that wouldn't fix anything
since when we convert StreamHealthError to error it would still
result in a non-nil error: https://go.dev/play/p/1JDB0I910-4

So just drop the variable with an intermediate type, and set it
based on the result of errors.As instead of by errors.As.

internal/app/recordtester/continuous_record_tester.go

@@ -107,9 +107,9 @@ func (crt *continuousRecordTester) Start(fileName string, testDuration, pauseDur
 			msg := fmt.Sprintf(":rotating_light: Test of %s ended with err=%v errCode=%v", crt.host, err, es)
 			messenger.SendFatalMessage(msg)
 			glog.Warning(msg)
-			var sherr testers.StreamHealthError
-			if errors.As(err, &sherr) {
-				err = nil
+			var sherr error
+			if errors.As(err, &testers.StreamHealthError{}) {
+				sherr, err = err, nil
 			}
 			crt.sendPagerdutyEvent(rt, err, false)
 			crt.sendPagerdutyEvent(rt, sherr, true)