Fix undefined attribute in scenario test class

An attribute check is being performed: "if not self.image_ref"
but self.image_ref may not be defined at all, leading to the
following error. So, let's define it first so it can be properly
evaluated.

AttributeError: 'TestShareBasicOpsNFS' object
has no attribute 'image_ref'

TrivialFix

Change-Id: I0c454009b95c5cb0b6fc1304bb0cba1ff87c9fe9
1 file changed
tree: c93648f795a501fd61c0b832243126c0e48efdd6
  1. manila_tempest_tests/