Bug 1229845

Description of problem: 

Currently the doc https://gitlab.cee.redhat.com/jowilkin/red-hat-ceph-storage-administration-guide/blob/v1.3/cluster-size.adoc has instructions for adding the mons using "mon create" command. This is failing when user wants to add additional mon nodes to existing cluster. Need to add the instructions to "add" monitor nodes to an already working cluster to increase the count of mons.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. bring up the cluster with one mon
2. follow the above mentioned doc to add further mon nodes

Actual results:
[OSD11][INFO  ] Running command: ceph --cluster=ceph --admin-daemon /var/run/ceph/ceph-mon.OSD11.asok mon_status
[OSD11][ERROR ] admin_socket: exception getting command descriptions: [Errno 2] No such file or directory
[OSD11][WARNIN] monitor: mon.OSD11, might not be running yet
[OSD11][INFO  ] Running command: ceph --cluster=ceph --admin-daemon /var/run/ceph/ceph-mon.OSD11.asok mon_status
[OSD11][ERROR ] admin_socket: exception getting command descriptions: [Errno 2] No such file or directory
[OSD11][WARNIN] OSD11 is not defined in `mon initial members`
[OSD11][WARNIN] monitor OSD11 does not exist in monmap
[OSD11][WARNIN] neither `public_addr` nor `public_network` keys are defined for monitors
[OSD11][WARNIN] monitors may not be able to form quorum


Expected results:
mon nodes addition should be successful

Additional info:
Had a chat with John on this. To add additional monitor nodes one needs to use "ceph-deploy mon add <node1> <node2> ...."

Here is the difference b/w both options(from help text):
create
  Deploy monitors by specifying them like:

    ceph-deploy mon create node1 node2 node3

  If no hosts are passed it will default to use the `mon initial members`
  defined in the configuration.

add
  Add a monitor to an existing cluster:

    ceph-deploy mon add node1

I feel in the above mentioned doc, we should use "mon add" instead of "create"