foundation: Made RPC layer safe against thrown "CancelledKeyException". This...

foundation: Made RPC layer safe against thrown "CancelledKeyException". This resolves server crashes seen in the wild.

- Caught CancelledKeyException where necessary or specified it in throwing methods. In particular, it may be thrown by the following member methods of java.nio.channels.SelectionKey: interestOps(), interestOps(int), readyOps(), isReadable(), isWritable(), isConnectable(), isAcceptable()
- Replaced tabs with spaces.

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@3243 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534