misc: Use tempfile.mkstemp() instead of tempnam
misc: Use tempfile.mkstemp() instead of tempnam

tempnam() is considered an unsafe security risk because the filename
generated is easy to guess and can be symlinked in advance.  Use
mkstemp() instead.

Signed-off-by: Sam Lang <70ab3b98ad075c66e7d3501cb42b80a7e41da316@inktank.com>
Reviewed-by: Joe Buck <a95e51950b61b017a762bcc8a962bac0b1a073a0@gmail.com>

t-miyamae/teuthology,dmick/teuthology,ivotron/teuthology,ktdreyer/teuthology,dreamhost/teuthology,SUSE/teuthology,ceph/teuthology,caibo2014/teuthology,ktdreyer/teuthology,tchaikov/teuthology,tchaikov/teuthology,michaelsevilla/teuthology,zhouyuan/teuthology,t-miyamae/teuthology,dmick/teuthology,dmick/teuthology,yghannam/teuthology,michaelsevilla/teuthology,dreamhost/teuthology,robbat2/teuthology,SUSE/teuthology,ceph/teuthology,ivotron/teuthology,caibo2014/teuthology,SUSE/teuthology,robbat2/teuthology,yghannam/teuthology,zhouyuan/teuthology