Description of problem:
While running ansible playbook with 3.1 latest build,(http://download-node-02.eng.bos.redhat.com/composes/auto/ceph-3.1-rhel-7/RHCEPH-3.1-RHEL-7-20180521.ci.0/), ansible-playbook failed with:
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TASK [ceph-mon : make sure pg num is set for cephfs pools] *********************
task path: /usr/share/ceph-ansible/roles/ceph-mon/tasks/check_mandatory_vars.yml:10
Tuesday 22 May 2018  02:49:18 -0400 (0:00:00.019)       0:00:54.842 *********** 

2018-05-22 06:49:21,680 - ceph.ceph - INFO - failed: [ceph-sshreeka-run775-node1-monmgrinstaller] (item={u'name': u'cephfs_data', u'pgs': u''}) => {"changed": false, "item": {"name": "cephfs_data", "pgs": ""}, "msg": "You must set pg num for your cephfs pools, see the cephfs_pools variable."}
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While running cephfs regression automation, I hit this issue. I used following configs:
            ceph_test: True
            ceph_origin: distro
            ceph_stable_release: luminous
            ceph_repository: rhcs
            osd_scenario: collocated
            osd_auto_discovery: False
            journal_size: 1024
            ceph_stable: True
            ceph_stable_rh_storage: True
            public_network: 172.16.0.0/12
            fetch_directory: ~/fetch
            copy_admin_key: true
            ceph_conf_overrides:
                global:
                  osd_pool_default_pg_num: 64
                  osd_default_pool_size: 2
                  osd_pool_default_pgp_num: 64
                  mon_max_pg_per_osd: 1024
                mon:
                  mon_allow_pool_delete: true
                  debug mon: 20
                mds:
                  mds_bal_split_size: 100
                  mds_bal_merge_size: 5
                  mds_bal_fragment_size_max: 10000
                  debug mds: 20
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Version-Release number of selected component (if applicable):
ceph : ceph-12.2.5-12.el7cp
os: Red Hat Enterprise Linux Server release 7.5 (Maipo)

How reproducible:
Always

Steps to Reproduce:
1.Try to setup ceph cluster with 3.1 build with configs mentioned above(Same configs were working good with previous builds.
2. Setup ceph-ansbile and run playbook(All these steps are running by automation)

Actual results:
Playbook failed with:TASK [ceph-mon : make sure pg num is set for cephfs pools] 
Expected results:
Cluster should setup without any issues.

Additional info:
Complete log of ceph-ansible playbook: http://magna002.ceph.redhat.com/cephci-jenkins/cephci-run-1526971098246/ceph_ansible_0.log