Avoid deleting created dropins folder before checkpoint

If a dropins folder is created before checkpoint there are
cases where the folder could be in the middle of being processed
when a checkpoint happens.  Deleting such a directory that is
in the middle of being monitored (i.e. getting a file listing)
will prevent the process from being restored successfuly by
criu.

This fix avoids deleting such directories created before a
checkpoint.  This allows the process to be restored multiple times.

Author: tjwatson

dev/com.ibm.ws.app.manager/src/com/ibm/ws/app/manager/internal/monitor/DropinMonitor.java

@@ -49,6 +49,8 @@
 import com.ibm.wsspi.kernel.service.utils.FilterUtils;
 import com.ibm.wsspi.kernel.service.utils.FrameworkState;
 
+import io.openliberty.checkpoint.spi.CheckpointPhase;
+
 /**
  * App manager file monitoring service which monitors a given directory for applications being added/deleted and starts/stops them as
  * appropriate.
@@ -474,7 +476,17 @@ private File updateMonitoredDirectory(String newMonitoredFolder) {
                 _monitors.clear();
 
                 if (!!!newDir.exists()) {
-                    createdMonitoredDir.set(newDir.mkdirs());
+                    boolean successfulMkDirs = newDir.mkdirs();
+                    if (CheckpointPhase.getPhase().restored()) {
+                        createdMonitoredDir.set(successfulMkDirs);
+                    } else {
+                        // Any created dropins directory created before checkpoint we want to avoid
+                        // deleting on shutdown.
+                        // The directory may be in the middle of being monitored during checkpoint.
+                        // Deleting such a directory on shutdown potentially can prevent the process
+                        // from being restored subsequent times.
+                        createdMonitoredDir.set(false);
+                    }
                 }
             } else {
                 oldDir = null;