convert nuke-on-error to boolean
convert nuke-on-error to boolean

Signed-off-by: Loic Dachary <bbaf4d8054803eb9fe7105066343d3847dccdd87@dachary.org>

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