Changed lsm io operation callback such that actions can be taken before and after executing the operation. This mechanism is going to be used by Asterix to inject the last lsn into components.

git-svn-id: https://hyracks.googlecode.com/svn/branches/hyracks_lsm_tree@2412 123451ca-8445-de46-9d55-352943316053
10 files changed