builtin-remote: make rm() use properly named variable to hold return value

"i" is a loop counter and should not be used to hold a return value; use
"result" instead which is consistent with the rest of builtin-remote.c.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>