ban lurker skips objects

[nigoroll]

pro-forma bug for fix ready to go in:

93d8050 made execution of ban_lurker_test_ban() conditional on bd != b, which effectively caused objects hanging off bans below request bans to not get tested against relevant bans.

Because object bans (from the obans list) are being marked completed, the objects which were skipped would also be missed to get evaluated against the relevant bans at lookup time unless they were evaluated in request context. So, in effect, we would simply miss to test bans.

Demo:

slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ varnishd -a 127.0.0.1:8080 -f /tmp/t.vcl 
Debug: Version: varnish-trunk revision 1262038523db35653e97977fc874fbf8ae92b41b
Debug: Platform: Linux,4.9.0-9-amd64,x86_64,-jnone,-sdefault,-sdefault,-hcritbit
Debug: Child (29983) Started
slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ n=0
slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ curl -sI localhost:8080/n$n >/dev/null ; varnishadm ban obj.http.c1 == n$((n++)) ; varnishadm ban.list

Present bans:
1559149084.719650     0 -  obj.http.c1 == n0
1559149065.981858     1 C  

slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ curl -sI localhost:8080/n$n >/dev/null ; varnishadm ban req.http.c1 == n$((n++)) ; varnishadm ban.list

Present bans:
1559149101.770700     0 -  req.http.c1 == n1
1559149084.719650     1 -  obj.http.c1 == n0
1559149065.981858     1 C  

slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ curl -sI localhost:8080/n$n >/dev/null ; varnishadm ban req.http.c1 == n$((n++)) ; varnishadm ban.list

Present bans:
1559149105.659101     0 -  req.http.c1 == n2
1559149101.770700     1 -  req.http.c1 == n1
1559149084.719650     1 -  obj.http.c1 == n0
1559149065.981858     1 C  

slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ varnishadm ban obj.status != 0

slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ varnishadm ban.list
Present bans:
1559149116.432023     0 -  obj.status != 0
1559149105.659101     0 -  req.http.c1 == n2
1559149101.770700     1 -  req.http.c1 == n1
1559149084.719650     1 -  obj.http.c1 == n0
1559149065.981858     1 C  

slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ varnishadm param.set ban_lurker_age 0.1

slink@haggis:~/Devel/varnish-git/varnish-cache ((126203852...))$ varnishadm ban.list
Present bans:
1559149116.432023     0 -  obj.status != 0
1559149105.659101     0 -  req.http.c1 == n2
1559149101.770700     1 -  req.http.c1 == n1
1559149084.719650     2 C