[TACHYON-220] WIP Comments describing issues and possible solutions 

Some initial comments to help improve the performance of master info. From what I gather there is locking on stack local objects that are never really put back into the map. I would appreciate suggestions before implementing it, hence the WIP tag.
Objects are passed by value. Maybe again we are spitting hairs on terminology of "reference" as people do when comparing c, c++, Java. The point is (also mentioned below)

 Inode inode = mFileIdToInodes.get(fileId);

change inodes as much as you like within this thread, it is inaccessible to another thread. Therefore the shared mFileIdToInodes map "references/has in the map/contains a version of" inodes that is *unchanged* until the current thread does a put(). Whether it is a concurrent map or not. Therefore why synchronise to modify inodes? 

http://www.programmerinterview.com/index.php/java-questions/does-java-pass-by-reference-or-by-value/