Fix race in waitForTraceCountAlive: check count before liveness

The liveness check fired before the trace count check, so a normal
process exit after delivering all traces was treated as a failure.
Check traceCount >= count first and return early if satisfied.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: bm1549

dd-smoke-tests/log-injection/src/test/groovy/datadog/smoketest/LogInjectionSmokeTest.groovy

@@ -358,6 +358,11 @@ abstract class LogInjectionSmokeTest extends AbstractSmokeTest {
         if (traceDecodingFailure != null) {
           throw traceDecodingFailure
         }
+        // Check the count BEFORE liveness — the process may have exited normally
+        // after delivering all traces, and we don't want to treat that as a failure.
+        if (traceCount.get() >= count) {
+          return
+        }
         if (testedProcess != null && !testedProcess.isAlive()) {
           def lastLines = tailProcessLog(20)
           throw new AssertionError(