bisect: avoid tailing CR characters from revision in replay

bisect: avoid tailing CR characters from revision in replay

6c722cbe5a (bisect: allow CRLF line endings in "git bisect replay"
input, 2020-05-07) includes CR as a field separator, but relies on
it not being included in the last field, which breaks at least when
running under OpenBSD 6.7's sh.

Instead of just assume the CR will get swallowed, read the rest of
the line into an otherwise unused variable and ignore it everywhere
except on the call for git bisect start, where it matters.

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>