elm_entry: fix wrong displayed scrollbars
the scrolbars have been displayed wrongly before. Reason for this is
that the theme displays the bars per default, the code however works
with hidden by default. This was worked arround before with the fact
that we are explicitly hiding the vbar/hbar before.
The reason this previous code was not working proberly is that entry
decided to retheme a object that was already set to the interface
scrollable object. Which means, it was not detected by the code. With
the newly introduced reset function you can tell the interface, that you
have changed the group, signals will be emitted accordingly.
Reviewed-by: Cedric BAIL <email@example.com>
Differential Revision: https://phab.enlightenment.org/D10622