cleanup: consistently use local variable instead of attribute

Signed-off-by: Jelmer Vernooij <jelmer@samba.org>
send_pack: simplify filtering of unsupported ref deletions

The previous implementation used filter() over a nontrivial nested
function with side-effects. A simple loop is a bit more readable.

Signed-off-by: Jelmer Vernooij <jelmer@samba.org>
send_pack: simplify condition guarding whether a pack is sent

Signed-off-by: Jelmer Vernooij <jelmer@samba.org>