extra/stb-tester.spec: Relax pylint < 1.0 requirement

We want people to be able to install the stb-tester RPM on systems like
Fedora 19 that have pylint 1.0. They just won't be able to use the new
`stbt lint` tool (due to bugs with pylint, and possibly differences in
the pylint plugin API; see 97eada33 and 65a38380). Note that `stbt lint`
checks the pylint version and exits with a clear error message.
Bump stb-tester version to 0.17

Note that the version number in the RPM spec file was already set to
0.17 (in 96afe36d; we haven't released the RPM since then so we don't
need to bump the version or release numbers).