(#14283) Call Tempfile#close and #unlink separately

Previously, we were calling Tempfile#close! which under ruby 1.8.7
will call the finalizer's cleanup routine directly. That may raise an
exception, e.g. Errno::EACCES, if the process is unable to unlink the
file, i.e. Windows. In ruby 1.9, the Tempfile#close! method was
changed to provide the same semantics as #close followed by #unlink.
Rather than monkey patch Tempfile, we simply call close followed by
unlink explicitly.