[TESTBUG] TestCgroupMetrics.java fails after fix for JDK-8219562

Change were made in JDK-8219562 to osContainer_linux.cpp to correct the parsing of of the /proc/self/mountinfo file but corresponding changes to the Metrics API and Container tests need to be done to match this change.

Here is a proposed fix:

diff --git a/src/java.base/linux/classes/jdk/internal/platform/cgroupv1/SubSystem.java b/src/java.base/linux/classes/jdk/internal/platform/cgroupv1/SubSystem.java
--- a/src/java.base/linux/classes/jdk/internal/platform/cgroupv1/SubSystem.java
+++ b/src/java.base/linux/classes/jdk/internal/platform/cgroupv1/SubSystem.java
@@ -60,7 +60,7 @@
                     path = mountPoint;
                 }
                 else {
- if (root.indexOf(cgroupPath) == 0) {
+ if (cgroupPath.indexOf(root) == 0) {
                         if (cgroupPath.length() > root.length()) {
                             String cgroupSubstr = cgroupPath.substring(root.length());
                             path = mountPoint + cgroupSubstr;
diff --git a/test/lib/jdk/test/lib/containers/cgroup/MetricsTester.java b/test/lib/jdk/test/lib/containers/cgroup/MetricsTester.java
--- a/test/lib/jdk/test/lib/containers/cgroup/MetricsTester.java
+++ b/test/lib/jdk/test/lib/containers/cgroup/MetricsTester.java
@@ -85,7 +85,7 @@
                 String mountPoint = paths[1];
                 if (root != null && cgroupPath != null) {
                     if (root.equals("/")) {
- if (cgroupPath.equals("/")) {
+ if (!cgroupPath.equals("/")) {
                             finalPath = mountPoint + cgroupPath;
                         } else {
                             finalPath = mountPoint;
@@ -94,7 +94,7 @@
                         if (root.equals(cgroupPath)) {
                             finalPath = mountPoint;
                         } else {
- if (root.indexOf(cgroupPath) == 0) {
+ if (cgroupPath.indexOf(root) == 0) {
                                 if (cgroupPath.length() > root.length()) {
                                     String cgroupSubstr = cgroupPath.substring(root.length());
                                     finalPath = mountPoint + cgroupSubstr;
@@ -103,7 +103,7 @@
                         }
                     }
                 }
- subSystemPaths.put(subSystem, new String[]{finalPath});
+ subSystemPaths.put(subSystem, new String[]{finalPath, mountPoint});
             }
         }
     }