Add rest_api, a new task that starts up /usr/bin/ceph-rest-api running as a daemon.
Add rest_api, a new task that starts up /usr/bin/ceph-rest-api running
as a daemon.

Fixes: 5613
Signed-off-by: Warren Usui <021fe6d8989d7bdb08c8700d8c426ea80a140097@inktank.com>

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