Fix issue in adding RAW disk in block storage domain (#3432)

By default, sparse option is true in ovirt. So the raw disk
    creation in a block storage domain will fail with error "Disk
    configuration (RAW Sparse) is incompatible with the storage domain
    type".

    The commit adds sparse option where it is send as False when
    format is raw and True when format is qcow2

lib/ansible/modules/extras/cloud/ovirt/ovirt_disks.py

@@ -65,7 +65,10 @@ options:
         default: 'virtio'
     format:
         description:
-            - "Format of the disk. Either copy-on-write or raw."
+            - Specify format of the disk.
+            - If (cow) format is used, disk will by created as sparse, so space will be allocated for the volume as needed, also known as I(thin provision).
+            - If (raw) format is used, disk storage will be allocated right away, also known as I(preallocated).
+            - Note that this option isn't idempotent as it's not currently possible to change format of the disk via API.
         choices: ['raw', 'cow']
     storage_domain:
         description:
@@ -168,6 +171,7 @@ class DisksModule(BaseModule):
             format=otypes.DiskFormat(
                 self._module.params.get('format')
             ) if self._module.params.get('format') else None,
+            sparse=False if self._module.params.get('format') == 'raw' else True,
             provisioned_size=convert_to_bytes(
                 self._module.params.get('size')
             ),
@@ -198,7 +202,6 @@ class DisksModule(BaseModule):
         return (
             equal(self._module.params.get('description'), entity.description) and
             equal(convert_to_bytes(self._module.params.get('size')), entity.provisioned_size) and
-            equal(self._module.params.get('format'), str(entity.format)) and
             equal(self._module.params.get('shareable'), entity.shareable)
         )
 
@@ -234,7 +237,6 @@ def main():
         vm_id=dict(default=None),
         size=dict(default=None),
         interface=dict(default=None,),
-        allocation_policy=dict(default=None),
         storage_domain=dict(default=None),
         profile=dict(default=None),
         format=dict(default=None, choices=['raw', 'cow']),