Convert the users of for_each_string_list to for_each_string_list_item macro

Convert the users of for_each_string_list to for_each_string_list_item macro

The rule for selecting the candidates for conversion is: if the callback
function returns only 0 (the condition for for_each_string_list to exit
early), than it can be safely converted to the macro.

A notable exception are the callers in builtin/remote.c. If converted, the
readability in the file will suffer greately. Besides, the code is not very
performance critical (at the moment, at least): it does output formatting of
the list of remotes.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>