[merge][#109520] gc of LockableFiles should not warn or unlock

[Martin Pool]

> http://bundlebuggy.aaronbentley.com/project/bzr/request/%3Ce01316480803181918s33ee9e47hf1c706e4044e27df%40mail.gmail.com%3E

The actual patch there was merged a while ago, but since it was a
plain diff BB had not noticed it.  That was to remove the
auto-unlocking and just give a warning when the lock leaks.

Looking at the warnings that do come out from the test suite, and that
I've seen in bug reports or interactive use, I think the majority if
not all are cases where we in fact cannot unlock.  For example they're
test cases for breaking a lock, where we unavoidably end up with an
object left behind that thinks it's still locked, but that can never
be unlocked.
(I can tell this because the message now includes a directory name
that matches up to the test.)

We could add a way to tell it to quietly abandon the lock, but I am
not sure that would be worth it.  So I am quite confident that
removing this gc message will not be hiding any real bugs in the test
suite.  (And there is a cost to having long-standing noise messages
from the tests, because it teaches people to ignore them...)

Outside the test suite, they tend to occur as a knock-on problem when
for example the transport has become unusable, and I'd say they're
generally clutter in the error message.

-- 
Martin <http://launchpad.net/~mbp/>