Wait longer for test lfs server to start.
Wait longer for test lfs server to start.

Also, back off on polling a bit after the first check to reduce any I/O
contention that might slow things down even more. Instead of 5 seconds,
this will wait up to about 60 seconds for files created by the test
server to appear. This allows very slow systems to be able to pass
tests.

Finally, add a message if the file doesn't appear to make it clear what
went wrong.

github/git-lfs,github/git-lfs,github/git-lfs