This change fixes the wrong parameter to set username of HNAS share
driver. The hitachi_hnas_username parameter has never been implemneted
and should be ``hitachi_hnas_user`` instead.
The user parameter is required by the driver, and the driver can't
start with the current wrong settings.
Because the configuration has been 'broken' since 2016, it'd be fair to
assume no user is using this actually. So the parameter is directly
renamed without deprecation step.
Closes-Bug: #1968514
Change-Id: I247dac538afc85544cc9e41d37a029806321e009
69bdd9e018