Remove unnecessary commit/uncommit

When the user reverts a commit, this causes the committed
word to be changed. The user usually then goes back to edit
that word.  Going back to edit causes an uncommit, so that
the editing actions are added onto the LogUnit containing
the operations used to construct the word.

But currently, reverting also involves its own
commit/uncommit pair, with the caller performing the
uncommit, and the commit happening inside the revert
command.  This may have been necessary in the past, when
revert was called in different situations, but is
unnecessary now.  Furthermore, the guarding conditions are
currently such that the uncommit doesn't always undo the
effects of the commit, corrupting the log output.

Change-Id: I74af41f4f1db2fcabfa496dcc4a2d7bd0af19b3a