Enable security group extension in PLUMgrid plugin

Implements: blueprint plumgrid-neutron-security-groups
Change-Id: I30392adff5e3250a1c4f9f1f04fc7e0587007226
Remove the Cisco Nexus monolithic plugin support

The Cisco Nexus monolithic plugin does not work without the Open
vSwitch plugin. The Open vSwitch plugin is scheduled to be removed
as per #1323729. This patch removes the Nexus Hardware switch
related code from devstack. The N1KV virtual switch related code
will still remain in the tree as it doesn't depend on Open vSwitch
plugin.

Closes-Bug: #1350387
Change-Id: I82ebb09c64589fc9b7bb790982541bc87c66e6e3
Update Horizon Neutron-related settings

- Horizon no longer has "enable_security_group" setting
  so we need to remove it.
- There is no need to set enable_lb/firewall/vpn to True
  when q-lbaas/q-fwaas/q-vpn is enabled because Horizon now checks if
  Neutron ext-list and enables corresponding dashboards accordingly.

Change-Id: I37073d73e4cba0103ab1a3d935302f1cd0ef73c5
Remove Nova v3 API endpoint

Nova v3 API has disappeared in Juno cycle, and we don't test the API
now on the gate since If63dcdb2d05aa0fab0b6848a1248b6678f1ee9ad .
This patch removes the endpoint of Nova v3 API.

Change-Id: I85f87b37558a15d1eaaa781b02fec5b02bd2ab44
Fix pkg name for mysql-connector-python on SUSE

The correct package name on SUSE distros is python-mysql-connector-python.

Change-Id: I5250356f782f149f87f3d0ffba3380911fa437be
Cleanup nova-cinder nova.conf section

Stop using deprecated conf names, don't override default values with
default values.

Change-Id: I2c7e0833a61926b9fc9b5de4e38fdd626501d78d
Stop setting nova.conf settings that mean nothing

* DEFAULT.fixed_range isn't a valid option in nova anymore
* DEFAULT.osci_compute_workers was never a thing, it should be
  DEFAULT.osapi_compute_workers

Change-Id: Ib08f3e20e4685b331385431276f890205fa76da6
Merge "Update Horizon Neutron-related settings"
Merge "Remove the Cisco Nexus monolithic plugin support"
Merge "Enable security group extension in PLUMgrid plugin"
Merge "Cleanup nova-cinder nova.conf section"
Merge "Fix pkg name for mysql-connector-python on SUSE"
Merge "Stop setting nova.conf settings that mean nothing"
Merge "Remove Nova v3 API endpoint"