[7.17] Make docker packaging test more resilient (#111205) (#111209)

* Make docker packaging test more resilient (#111205)

Wrap check for container shutdown log message in an `assertBusy()` to
deal with race conditions.

Closes #111132
# Conflicts:
#	muted-tests.yml
#	qa/os/src/test/java/org/elasticsearch/packaging/test/DockerTests.java

* Fix compile issue

qa/os/src/test/java/org/elasticsearch/packaging/test/DockerTests.java

@@ -1108,10 +1108,12 @@ public void test600Interrupt() throws Exception {
         int maxPid = processes.stream().map(i -> Integer.parseInt(i.trim())).max(Integer::compareTo).get();
 
         sh.run("bash -c 'kill -int " + maxPid + "'"); // send ctrl+c to all java processes
-        final Result containerLogsAfter = getContainerLogs();
 
-        assertThat("Container logs should contain stopping ...", containerLogsAfter.stdout, containsString("stopping ..."));
-        assertThat("No errors stdout", containerLogsAfter.stdout, not(containsString("java.security.AccessControlException:")));
-        assertThat("No errors stderr", containerLogsAfter.stderr, not(containsString("java.security.AccessControlException:")));
+        assertBusy(() -> {
+            final Result containerLogsAfter = getContainerLogs();
+            assertThat("Container logs should contain stopping ...", containerLogsAfter.stdout, containsString("stopping ..."));
+            assertThat("No errors stdout", containerLogsAfter.stdout, not(containsString("java.security.AccessControlException:")));
+            assertThat("No errors stderr", containerLogsAfter.stderr, not(containsString("java.security.AccessControlException:")));
+        });
     }
 }