Fix -Wformat compilation errors in tests

[sigmavirus24]

There were several warnings generated by formatting errors in the tests,
this corrects the format strings and silences the warnings.

[ingydotnet]

@sigmavirus24, could you explain how you got these warnings, or point to a
system showing them?

I applied your patch and ran make test but still got the same warnings (for
both make and `make test) as before the patch.

See: https://gist.github.com/anonymous/dbebcf632b91a54c4f25c7ceb79c4fcd

[sigmavirus24]

Using the dockerfiles in tree, I ran make clean && make after building a second time. Looks like you're running on OSX. I'll test that out tonight.

[sigmavirus24]

And if you look at Semaphore you'll see that it also doesn't have the warnings you've found. I want to slowly start adding more flags to our Makefile though until we have -Wall covered and then we can enable -Werror so that we prevent regression of them.

[sigmavirus24]

@ingydotnet I updated this. I can't find any format related warnings now on Ubuntu or macOS/OSX.

[ingydotnet]

@sigmavirus24, I'm still getting all the warnings on OSX

See: https://gist.github.com/693103baa4949eb2187810138a79d94b

Linux make and make test is warning free, but is also that way on
origin/master.

Confused.

[sigmavirus24]

Using your gist, I corrected the last of the -Wformat errors that either of us seem to be able to find.

[ingydotnet]

Looks good to me. Applied, pushed, thanks.