This reverts the default timeout for test cases back to 300 seconds.
The change in the release was quite blind because it did not anticipate
many existing tests to be slow enough to overflow the modified timeout
(30 seconds), specially in anita.
My plan to really fix this is to let test cases specify their sizes in
a declarative way instead of specifying timeouts in seconds (the timeout
being defined by atf-run on a size basis), so I'm not going to bother to
go over all existing tests trying to figure out which ones need a higher
timeout for now. It is just easier to revert.
9e95dfadb1