rev-parse: don't trim bisect refnames

rev-parse: don't trim bisect refnames

Using for_each_ref_in() with a full refname has always been
a questionable practice, but it became an error with
b9c8e7f2fb (prefix_ref_iterator: don't trim too much,
2017-05-22), making "git rev-parse --bisect" pretty reliably
show a BUG.

Commit 03df567fbf (for_each_bisect_ref(): don't trim
refnames, 2017-06-18) fixed this case for revision.c, but
rev-parse handles this option on its own. We can use the
same solution here (and piggy-back on its test).

Signed-off-by: Jeff King <redacted>
Acked-by: Michael Haggerty <redacted>
Signed-off-by: Junio C Hamano <redacted>