Add helper methods to test libraries

I'd like to add 2 helper methods to test library code. It'll help me clean up a testcase in closed code but should also be of use to engineers for future testcode development.

one method is in RMI testlibrary code. Another is in File/IO testlibrary code :

== RMI :
test/java/rmi/testlibrary/TestLibrary.java
checkIfRegistryRunning method to test if an rmiregisty process has started up and is serving requests. It can wait for a specified amount of time before giving up if no registry can be contacted on port on local system.

== Files/IO
FileUtils.deleteFileIfExistsWithRetry(Path path) method.

This method is identical to FileUtils.deleteFileWithRetry method except that it doesn't throw IOException if the file to delete doesn't exist.