internal: ignore binary junk in kernel logs
internal: ignore binary junk in kernel logs

NUL bytes can show up here after powercycle testing

Signed-off-by: Josh Durgin <51652c783f70f5b272ebd02f1fd20d3af7a2449f@inktank.com>

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