make test-mq-qdelete work reliably (issue1180)
if after a and b has been applied, their hash starts with c, then the test
would fail (because there would be a rev c which would be seen as "applied")
so probability of failure would be 2*1/16.
% qimport non-existing-file
abort: unable to read non-existing-file
% build diff with CRLF
adding b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% qimport CRLF diff
adding b.diff to series file
applying b.diff
Now at: b.diff