Originally BayModel#fixed_network was used for setting which
fixed_network was set to Bay [1].
But this attribute changed to setting fixed_network_cidr [2].
This patch removes mapping for fixed_network_cidr.
And also, fixed_network_cidr attribute will be add to
baymodel [3].
Magnum user want to specify fixed_network for bay, so I'll add
a mapping to template definition to set fixed_network
next patch.
[1]: bc3bc6190d/magnum/conductor/handlers/bay_k8s_heat.py (L101)
[2]: I624b95930f9eb506abfb2e29beea8d83878ea142
[3]: Ia74ed924b3058b4891775f34f1b9624774c02ddb
Change-Id: Ia9820213bcc0e2a451450dd014e774843b881fd1
Closes-Bug: #1536484