Description of problem:
Created 3 MDS server, after a while i again tried to create another mds server, but i missed to change the same name.

I am not seeing any error.

Version-Release number of selected component (if applicable):
ceph version 10.2.1-1.el7cp
ceph-mds-10.2.1-1.el7cp.x86_64

How reproducible:
Always

Steps to Reproduce:
1.Created 3 mds server.
ceph-deploy mds create 10.70.x.x:mds0
ceph-deploy mds create 10.70.x.x:mds1
ceph-deploy mds create 10.70.x.x:mds2
2.All 3 came up 
ps -ef |grep mds
ceph      87399      1  0 15:21 ?        00:00:00 /usr/bin/ceph-mds -f --cluster ceph --id mds0 --setuser ceph --setgroup ceph
ceph      87531      1  0 15:21 ?        00:00:00 /usr/bin/ceph-mds -f --cluster ceph --id mds1 --setuser ceph --setgroup ceph
ceph      87893      1  0 15:53 ?        00:00:00 /usr/bin/ceph-mds -f --cluster ceph --id mds2 --setuser ceph --setgroup ceph
root      88341   4041  0 16:32 pts/1    00:00:00 grep --color=auto mds
[root@cephqe3 ceph-ansible]# ceph mds stat
e7:, 3 up:standby

3.Again i re-ran the same command 

ceph-deploy mds create 10.70.x.x:mds2

[ceph_deploy.conf][DEBUG ] found configuration file at: /root/.cephdeploy.conf
[ceph_deploy.cli][INFO  ] Invoked (1.5.33): /usr/bin/ceph-deploy mds create 10.70.x.x:mds2
[ceph_deploy.cli][INFO  ] ceph-deploy options:
[ceph_deploy.cli][INFO  ]  username                      : None
[ceph_deploy.cli][INFO  ]  verbose                       : False
[ceph_deploy.cli][INFO  ]  overwrite_conf                : False
[ceph_deploy.cli][INFO  ]  subcommand                    : create
[ceph_deploy.cli][INFO  ]  quiet                         : False
[ceph_deploy.cli][INFO  ]  cd_conf                       : <ceph_deploy.conf.cephdeploy.Conf instance at 0x7f2f2ec6b950>
[ceph_deploy.cli][INFO  ]  cluster                       : ceph
[ceph_deploy.cli][INFO  ]  func                          : <function mds at 0x7f2f2ec482a8>
[ceph_deploy.cli][INFO  ]  ceph_conf                     : None
[ceph_deploy.cli][INFO  ]  mds                           : [('10.70.x.x', 'mds2')]
[ceph_deploy.cli][INFO  ]  default_release               : False
[ceph_deploy.mds][DEBUG ] Deploying mds, cluster ceph hosts 10.70.x.x:mds2
[10.70.x.x][DEBUG ] connected to host: 10.70.x.x 
[10.70.x.x][DEBUG ] detect platform information from remote host
[10.70.x.x][DEBUG ] detect machine type
[ceph_deploy.mds][INFO  ] Distro info: Red Hat Enterprise Linux Server 7.2 Maipo
[ceph_deploy.mds][DEBUG ] remote host will use systemd
[ceph_deploy.mds][DEBUG ] deploying mds bootstrap to 10.70.x.x
[10.70.x.x][DEBUG ] write cluster configuration to /etc/ceph/{cluster}.conf
[10.70.x.x][DEBUG ] create path if it doesn't exist
[10.70.x.x][INFO  ] Running command: ceph --cluster ceph --name client.bootstrap-mds --keyring /var/lib/ceph/bootstrap-mds/ceph.keyring auth get-or-create mds.mds2 osd allow rwx mds allow mon allow profile mds -o /var/lib/ceph/mds/ceph-mds2/keyring
[10.70.x.x][INFO  ] Running command: systemctl enable ceph-mds@mds2
[10.70.x.x][INFO  ] Running command: systemctl start ceph-mds@mds2
[10.70.x.x][INFO  ] Running command: systemctl enable ceph.target

Actual results:
Again creating same mds server is not giving any error message, and the mds 2 is having same pid after re-running the command.

ceph      87893      1  0 15:53 ?        00:00:00 /usr/bin/ceph-mds -f --cluster ceph --id mds2 --setuser ceph --setgroup ceph

Expected results:
1. It should throw an Error, when i am creating the MDS server same named.
2. If it succeeds, it should run as a new process.

Additional info:
NA