FSLoader only returns value at the beginning

FSLoader implements Backup store for db CacheManager. In the initial load, it reads all the lines of the file, line by line, and returns a Map of key-value pairs with a key-value pair for every line. It returns data only on the initial load and thereafter it returns null for any key lookup. Also, there is no need to load all the data in the file and return it if the primary cache cannot hold all the entries. These issues need to be addressed and it also helps if the CacheManager supplies meta-information such as how much information should be loaded and returned in the initial load.