Temporary workaround for config generator

Current oslo.config.cfg.Opt doesn't support operator '=='. So use 'not
!=' instead. This is a temporary workaround before the newly released
oslo.config support the operator '=='.

Partial-Bug: 1262148

Change-Id: I19279cd211594bb107777d6b98ebe6990063ebc7
Merge "Temporary workaround for config generator"