Fix current term and handle command invocation in leader for previous term entries.

- Update current term upon log load during init.
- While committing log index, in case of leader, for previous term
  entries, there will not be any blocking client. Command should be
  invoked even in this case. One such scenario is when log file is
  loaded and logCommitIndex is done for current term entry, all the
  previous entries are also committed. For leader, without the fix,
  command invocation was missing.