@Michael Arndt : 

Thank you for raising this. Yes, its ideal to use DNS name which is present in nfs_shares_config file. 

I tried mounting the share via DNS name, something like this: 

root@linux-box:~# cat /etc/cinder/nfs_shares
msaravan-openstack-vm.netapp.com:/cinder1
root@linux-box:~#

Without code change, the destination share looks like this :
10.1.1.1:/msaravan_cinder1.

I am able to hit the code flow you suggested. With the code change you have proposed, the destination 
share would look like this, and this is exactly matching with what is configured in NFS shares file:

msaravan-openstack-vm.netapp.com:/cinder1


When the copy file is invoked with the existing code, the variable dst_share is never used. You can see that below. 

self._copy_file(img_file, img_file, src_volume, src_vserver,
                                dest_share_path, dest_vserver,
                                dest_backend_name=self.backend_name,
                                dest_file_name=tmp_img_file)


Also the copy takes place using below parameters via NetApp ZAPI call, and its always successful:

job_uuid = self.zapi_client.start_file_copy(
            file_name, dest_ontap_volume, src_ontap_volume=src_ontap_volume,
            dest_file_name=dest_file_name)


The actual values passed in the above method are : 

file_name: d4ed4356-cfeb-474d-b254-90a0501352c9 
dest_ontap_volume : msaravan_cinder1 
src_ontap_volume: glance_flexvol
dest_file_name: b16dbe27-f47b-4449-935d-f084b26a5c8c 


I also see that the img-cache is created successfully. 

root@scspo2853621001:/opt/stack/data/cinder/mnt/99f446539c9f7c9374044cec5d11981a# ls
8107ad2a-89ec-4241-8ce9-cb51340c51b3            volume-42efa05a-6416-4ef4-ac67-ac37ca875efc  volume-7f4e04c3-5c50-4f31-a16c-0c1be8e6d5fd
a8d760cd-8ba0-4969-ae2b-1a8c566223eb            volume-44d52221-8d25-4735-ac4e-d6a58f418295  volume-8100d537-92c4-4e9d-81f0-e16ee85b7e0f
img-cache-d4ed4356-cfeb-474d-b254-90a0501352c9  volume-4f308896-11a4-4748-b2ce-080bf9bc2578  volume-a60a63a0-578b-48ba-90ab-789d24b4a3c7
volume-092e044d-ce2c-4f66-a225-ec2b1df89fd9     volume-4fefa610-b056-4ba5-a999-7453f269275a  volume-af801dd8-43f4-44bb-88b2-8b1b325f0720
volume-11f3baf7-d11d-4d4a-a583-1e230c66f01f     volume-535d5bf1-9322-4a7d-af32-91a363ab8cdc  volume-bf342b6b-9175-4238-8cc6-242f562cab78
volume-12bf8500-1d77-439c-a0d7-9d3dc3031770     volume-53661b03-07f2-408f-9b16-61dfb8e99e2d  volume-c75b91c9-3f19-4ac9-b7b2-9177aec83b0e
volume-2243360e-c29a-4036-9ec1-6d9fcc966519     volume-597176a1-be2f-41f3-9aa2-b14b5ffbbffe  volume-e469a1e5-1420-485d-b47e-b351b90d6e80
volume-34b23b72-b039-4523-bdd0-598b5a9d0c18     volume-5a9f7d9a-3a4a-4cca-9a72-82d804988608  volume-ebb9f74c-7d17-49dd-afe7-68c1dcba9339
volume-3842a0e6-5590-4306-a477-cd32405c861a     volume-6c7f7382-54f9-4214-971d-e8606e1ac6ab  volume-f98bc97b-1a82-4cd9-8811-6b3ece3d76aa
volume-3c77da2d-510e-47a2-91a8-4b87e2d601e9     volume-6f4440a4-41cf-4abf-9850-2f35f9c6d8e8
volume-3ce2f35b-4112-460a-a75b-ec5772ec4a24     volume-7863bb84-f898-4695-97c9-2f600eb6c01a
root@scspo2853621001:/opt/stack/data/cinder/mnt/99f446539c9f7c9374044cec5d11981a#


Logs:
DEBUG cinder.volume.drivers.netapp.dataontap.nfs_cmode [None req-5cf0709a-ecee-4aa7-b51f-f3caaa57f39e admin None] Copied image d4ed4356-cfeb-474d-b254-90a0501352c9 to tmp file 0f03e0dc-8507-42ea-a723-e05bcaa01c3b. {{(pid=3431250) _copy_from_img_service /opt/stack/cinder/cinder/volume/drivers/netapp/dataontap/nfs_cmode.py:801}}
DEBUG cinder.volume.drivers.netapp.dataontap.nfs_cmode [None req-5cf0709a-ecee-4aa7-b51f-f3caaa57f39e admin None] Image will be converted to raw d4ed4356-cfeb-474d-b254-90a0501352c9. {{(pid=3431250) _copy_from_img_service /opt/stack/cinder/cinder/volume/drivers/netapp/dataontap/nfs_cmode.py:813}}
DEBUG oslo_concurrency.processutils [None req-6ee03a8d-5c51-459a-abc5-244fccfd8d28 admin None] CMD "mv /opt/stack/data/cinder/mnt/a8953091bda09767c2e26dda472e47cb/3e448409-77d2-4c01-87a5-34aa0fc862cb /opt/stack/data/cinder/mnt/a8953091bda09767c2e26dda472e47cb/img-cache-d4ed4356-cfeb-474d-b254-90a0501352c9" returned: 0 in 0.630s {{(pid=3000873) execute /usr/local/lib/python3.8/dist-packages/oslo_concurrency/processutils.py:422}}


If its consistently reproducible for you, can you please share the exact error you have seen when the img-cache is created ? Or if you find my steps wrong, please correct that so that I'll re-try it with the path you suggested.