Failing tests are not re-triggered when package with failures is re-uploaded

Case which happened today.

 - gtk+3.0 was uploaded
 - this triggered a test run of gvfs, which failed
 - gvfs was uploaded to fix this failure
 - gtk+3.0's trigger of gvfs did not get updated

Given that we are trying to install as little as possible from -proposed, the
run for gvfs itself would not get the new gtk+3.0. We need to run gvfs's tests
with a trigger of gtk+3.0.

That is, for an upload of a package P, re-trigger all triggers which were for P
and which failed. Don't do this in the other way (pass -> fail), since a new
failure can't be the fault of P here.