sha1_file: restore OBJECT_INFO_QUICK functionality

sha1_file: restore OBJECT_INFO_QUICK functionality

Support for the OBJECT_INFO_QUICK flag in sha1_object_info_extended()
was added in commit dfdd4afcf9 ("sha1_file: teach
sha1_object_info_extended more flags", 2017-06-26) in order to support
commit e83e71c5e1 ("sha1_file: refactor has_sha1_file_with_flags",
2017-06-26), but it was inadvertently removed in commit 8b4c0103a9
("sha1_file: support lazily fetching missing objects", 2017-12-08).

Restore this functionality.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>