Description of problem:
  Creating cluster via USM API or web UI sometime fails with error:
    Failed. error: json: cannot unmarshal array into Go value of type models.AddClusterRequest


Version-Release number of selected component (if applicable):
USM server:
  ceph-0.94.5-9.el7cp.x86_64
  ceph-ansible-1.0.1-1.20160307gitb354445.el7.noarch
  ceph-common-0.94.5-9.el7cp.x86_64
  redhat-ceph-installer-0.2.3-1.20160304gitb3e3c68.el7.noarch
  rhscon-ceph-0.0.6-14.el7.x86_64
  rhscon-core-0.0.8-14.el7.x86_64
  rhscon-ui-0.0.23-1.el7.noarch
Ceph MON:
  ceph-0.94.5-9.el7cp.x86_64
  ceph-common-0.94.5-9.el7cp.x86_64
  ceph-mon-0.94.5-9.el7cp.x86_64
  rhscon-agent-0.0.3-3.el7.noarch
Ceph OSD:
  rhscon-agent-0.0.3-3.el7.noarch
  
How reproducible:
  often 70%

Steps to Reproduce:
1. Prepare bunch of hosts (1 USM server, 3 monitors and 4 osd in my case).
2. Install and preconfigure them accordingly to documentation.
3. Try to create cluster via REST API or web UI

Actual results:
  Sometimes the cluster creation task fails with error:
    Failed. error: json: cannot unmarshal array into Go value of type models.AddClusterRequest

Expected results:
  Cluster is properly created without any error.


Additional info:
  Failed task detail
  # 	Execution Steps 	Result
  1 	Started the task for cluster creation: 04ad6729-b424-4f25-9cf0-6e322cb15512 	Mar 22 2016, 01:10:32 PM
  2 	Installing packages 	Mar 22 2016, 01:10:32 PM
  3 	Installing packages done. Starting Cluster Creation. 	Mar 22 2016, 01:11:09 PM
  4 	Failed. error: json: cannot unmarshal array into Go value of type models.AddClusterRequest 	Mar 22 2016, 01:11:09 PM