bloom: rename function operates on bloom_key

bloom: rename function operates on bloom_key

git code style requires that functions operating on a struct S
should be named in the form S_verb. However, the functions operating
on struct bloom_key do not follow this convention. Therefore,
fill_bloom_key() and clear_bloom_key() are renamed to bloom_key_fill()
and bloom_key_clear(), respectively.

Signed-off-by: Lidong Yan <502024330056@smail.nju.edu.cn>
Signed-off-by: Junio C Hamano <gitster@pobox.com>