8222533: jtreg test jdk/internal/platform/cgroup/TestCgroupMetrics.java fails on SLES12.3 linux ppc64le machine

Reviewed-by: mseledtsov, dholmes

src/java.base/linux/classes/jdk/internal/platform/cgroupv1/SubSystem.java

@@ -108,7 +108,7 @@ public class SubSystem {
         try {
             List<String> lines = Files.readAllLines(Paths.get(subsystem.path(), param));
             for (String line: lines) {
-                if (line.contains(match)) {
+                if (line.startsWith(match)) {
                     retval = conversion.apply(line);
                     break;
                 }