reproducable test librarian (and sometimes memcached) leak

If I run just bin.test -vvt lib/lp/soyuz/tests/../doc/closing-bugs-from-changelogs.txt
with it failing as in rev 12447 of lp:~lifeless/launchpad/bug-279513
the librarian process leaks:

robertc 12054 0.0 0.1 122996 2140 pts/0 Sl+ 12:19 0:00 memcached -m 1 -l 127.0.0.1 -p 11242 -U 11242
robertc 12053 0.5 15.2 486008 183152 ? Sl 12:19 0:00 /usr/bin/python2.6 -Wignore::DeprecationWarning /home/robertc/launchpad/lp-branches/working/bin/twistd -o -y /home/robertc/launchpad/lp-branches/working/daemons/librarian.tac