Fix t5516-fetch for systems where `wc -l` outputs whitespace.

Fix t5516-fetch for systems where `wc -l` outputs whitespace.

When wc outputs whitespace, the test "$(command | wc -l)" = 1 is
broken because "   1" != "1".  Let the shell eat the whitespace by
using test 1 = $(command | wc -l) instead.

Signed-off-by: Brian Gernhardt <benji@silverinsanity.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>