NetWorker: Docker contrainer NetWorker client backup fails with error savefs: fail

NetWorker schedule backup fails for Docker container client
Error:
<client name>:savefs failed.
<client name>:savefs See the file '/nsr/logs/policy/<policy>/<workflow/backup_<jobid>_logs/<jobid>.log' for command output.
Stopped processing of the save set <cleint name>:<save set> because the savefs job job terminated with an error.
Job <jobid> host: <client name> savepoint: <save set> had ERROR indication(s) at completion
<client name>:<save set> abandoned.
Client '<client name>' is being skipped because no savesets of this client have been backed up as part of the backup action.
Action backup traditional 'backup' with job id <job id> is exiting with status 'failed', exit code 1

NetWorker client in Docker container is not officially supported in current release. 
Docker container has a overlay file system. It doesn't have /etc/fstab.

It works by a workaround to create a /etc/fstab in docker container. The RFE NW-I-1396 is in product management for review
ESC 37659 - Request NetWorker support for Docker container client backup
Workaround: 
Login into Docker container as root and run, 
# cp /etc/mtab /etc/fstab