[BUG] Fixing org.opensearch.monitor.os.OsProbeTests > testLogWarnCpuM…

…essageOnlyOnes when cgroups are available but cgroup stats is not (#3448) (#3464)

Signed-off-by: Andriy Redko <andriy.redko@aiven.io>
(cherry picked from commit 1b93cf8)

Co-authored-by: Andriy Redko <andriy.redko@aiven.io>

server/src/test/java/org/opensearch/monitor/os/OsProbeTests.java

@@ -32,6 +32,8 @@
 
 package org.opensearch.monitor.os;
 
+import static org.hamcrest.CoreMatchers.not;
+import static org.hamcrest.CoreMatchers.nullValue;
 import static org.hamcrest.Matchers.allOf;
 import static org.hamcrest.Matchers.anyOf;
 import static org.hamcrest.Matchers.both;
@@ -296,8 +298,12 @@ List<String> readSysFsCgroupCpuAcctCpuStat(String controlGroup) throws IOExcepti
             }
         };
 
-        assumeThat("CGroups are not available", noCpuStatsOsProbe.areCgroupStatsAvailable(), is(true));
-        noCpuStatsOsProbe.osStats();
+        assumeThat("CGroups are available", noCpuStatsOsProbe.areCgroupStatsAvailable(), is(true));
+        OsStats osStats = noCpuStatsOsProbe.osStats();
+
+        // Depending on CGroups v1/v2, the cgroup stats may not be available
+        assumeThat("CGroup is available", osStats.getCgroup(), is(not(nullValue())));
+
         // no nr_throttled and throttled_time
         verify(logger, times(2)).warn(anyString());
         reset(logger);