kernel: loop reconnecting in case we race with shutdown
kernel: loop reconnecting in case we race with shutdown

Previously, if we reconnected before shutdown completed we asserted
that the kernel did not boot into the new version, when we just needed
to wait for the machine to reboot.

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