Fixing timestamp issue for mongodb file system

Author: PicoCreator

src/main/java/picoded/dstack/mongodb/MongoDB_FileWorkspaceMap.java

@@ -801,7 +801,7 @@ public long backend_createdTimestamp(final String oid, final String filepath) {
 	 */
 	public long backend_modifiedTimestamp(final String oid, final String filepath) {
 		// Lets build the query for the "root file"
-		Bson query = Filters.eq("filename", filepath);
+		Bson query = Filters.eq("filename", oid + "/" + filepath);
 
 		// Lets prepare the search
 		GridFSFindIterable search = gridFSBucket.find(query).limit(1);