allow to concatenate a bunch of keyrings for seeing new monitors


Reference issue tracker.ceph.com/issues/9118
Output warning of duplicate keyrings:

    ceph-deploy mon --keyrings keyrings create-initial
    [ceph_deploy.conf][DEBUG ] found configuration file at: /Users/alfredo/.cephdeploy.conf
    [ceph_deploy.cli][INFO  ] Invoked (1.5.11): /Users/alfredo/.virtualenvs/ceph-deploy/bin/ceph-deploy mon --keyrings keyrings create-initial
    [ceph_deploy.mon][INFO  ] concatenating keyrings to seed remote monitors
    [ceph_deploy.mon][DEBUG ] /Users/alfredo/tmp/foo/keyrings
    [ceph_deploy.mon][DEBUG ] ['/Users/alfredo/tmp/foo/keyrings/ceph.bootstrap-mds.keyring', '/Users/alfredo/tmp/foo/keyrings/ceph.bootstrap-osd.keyring', '/Users/alfredo/tmp/foo/keyrings/ceph.client.admin.keyring', '/Users/alfredo/tmp/foo/keyrings/ceph.mon.keyring', '/Users/alfredo/tmp/foo/keyrings/foo.mon.keyring']
    [ceph_deploy.mon][INFO  ] adding entity "client.bootstrap-mds" from keyring /Users/alfredo/tmp/foo/keyrings/ceph.bootstrap-mds.keyring
    [ceph_deploy.mon][INFO  ] adding entity "client.bootstrap-osd" from keyring /Users/alfredo/tmp/foo/keyrings/ceph.bootstrap-osd.keyring
    [ceph_deploy.mon][INFO  ] adding entity "client.admin" from keyring /Users/alfredo/tmp/foo/keyrings/ceph.client.admin.keyring
    [ceph_deploy.mon][INFO  ] adding entity "mon." from keyring /Users/alfredo/tmp/foo/keyrings/ceph.mon.keyring
    [ceph_deploy.mon][WARNIN] will not add keyring: /Users/alfredo/tmp/foo/keyrings/foo.mon.keyring
    [ceph_deploy.mon][WARNIN] entity "mon." from keyring /Users/alfredo/tmp/foo/keyrings/foo.mon.keyring is a duplicate
    [ceph_deploy.mon][WARNIN] already present in keyring: /Users/alfredo/tmp/foo/keyrings/ceph.mon.keyring
    [ceph_deploy.mon][DEBUG ] Deploying mon, cluster ceph hosts node2
    [ceph_deploy.mon][DEBUG ] detecting platform for host node2 ...
    [node2][DEBUG ] connected to host: node2
    [node2][DEBUG ] detect platform information from remote host
    [node2][DEBUG ] detect machine type
    [ceph_deploy.mon][INFO  ] distro info: CentOS 6.4 Final
    [node2][DEBUG ] determining if provided host has same hostname in remote
    [node2][DEBUG ] get remote short hostname
    [node2][DEBUG ] deploying mon to node2
    [node2][DEBUG ] get remote short hostname
    [node2][DEBUG ] remote hostname: node2
    [node2][DEBUG ] write cluster configuration to /etc/ceph/{cluster}.conf
    [node2][DEBUG ] create the mon path if it does not exist
    [node2][DEBUG ] checking for done path: /var/lib/ceph/mon/ceph-node2/done
    [node2][DEBUG ] create a done file to avoid re-doing the mon deployment
    [node2][DEBUG ] create the init path if it does not exist
    [node2][DEBUG ] locating the `service` executable...
    [node2][INFO  ] Running command: sudo /sbin/service ceph -c /etc/ceph/ceph.conf start mon.node2
    [node2][DEBUG ] === mon.node2 ===
    [node2][DEBUG ] Starting Ceph mon.node2 on node2...