Undo potentially confusing name change in packaging.

Undo potentially confusing name change in packaging.

This method was named reinitialize_command in distutils and accompanied
by a comment suggesting to change it to get_reinitialized_command.
Following that, I did the change for distutils2, but it proved
confusing: The Distribution object has an internal cache of command
objects, to make sure only one instance is ever used, and the name
get_reinitialized_command could suggest that the object returned was
independent of that cache, which it was not.  I’m reverting the name
change to make code clearer.