Description of problem:
-----------------------
Using gdeploy,unable to set the writePolicy of VDO volume to 'auto'. Gdeploy allows the value of 'sync' & 'async' for writePolicy

Version-Release number of selected component (if applicable):
--------------------------------------------------------------
gdeploy-2.0.2-22.el7rhgs

How reproducible:
-----------------
Always

Steps to Reproduce:
--------------------
1. Create a gdeploy conf file to create VDO volume and set the writePolicy to auto

Actual results:
---------------
gdeploy fails to set the writePolicy as 'auto'

Expected results:
-----------------
gdeploy should allow setting the value of writePolicy as 'auto'

Additional info:
----------------
Here is the sample config file
[hosts]
10.70.36.244

[vdo]
action=create
devices=sde
names=vdovol_test
logicalsize=18T
writepolicy=auto
slabsize=32G
emulate512=enabled

Here is the console output:

# gdeploy -c vdocreate.conf 

PLAY [gluster_servers] ********************************************************************************************************************************************************************************************

TASK [Create VDO with specified size] *****************************************************************************************************************************************************************************
failed: [10.70.36.244] (item={u'disk': u'/dev/sde', u'logicalsize': u'18T', u'name': u'vdovol_test'}) => {"changed": false, "item": {"disk": "/dev/sde", "logicalsize": "18T", "name": "vdovol_test"}, "msg": "value of writepolicy must be one of: sync,async, got: auto"}
	to retry, use: --limit @/tmp/tmpVnBih0/vdo-create.retry

PLAY RECAP ********************************************************************************************************************************************************************************************************
10.70.36.244               : ok=0    changed=0    unreachable=0    failed=1