ui-summary.c: Move urls variable into print_urls()

There's no need for this variable to be global. Printing the header in
print_urls() instead of print_url() allows for moving this variable into
print_urls() without having to pass any status to print_url().

Note that this only works as long as we don't call print_urls() more
than once.

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>