lineedit: fix tab-completion of filenames with spaces

lineedit: fix tab-completion of filenames with spaces

Using ash in busybox git version dea28e1e, tab completion doesn't seem
to work properly for filenames that have special characters (such as
spaces) in them. For example, with filenames "foo bar" and "foo zap",
typing "ls fo<TAB>" correctly expands to "ls foo\ ", but then
continuing to type "b<TAB>" will produce "ls foo\ bbar", which is not
correct (the 'b' is duplicated).

Signed-off-by: Mike Shal <marfey@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>