Kill 'Skipping unknown group key: firewall_driver' log trace

This is done by trying to import the option first. If this
does not work, emit a warning instead as in most cases this is
harmless for a number of reasons: a) the service might not
even need the opt; b) if things do break down the line, we'll
see bigger traces; c) it's not gonna be long for this legacy
quantum/neutron stuff to be removed altogether.

Closes-bug: 1210121

Change-Id: I34917da9cb6117ee1d42140621c742f503279b6b
NSX: Ensure gateway devices are usable after upgrade

The gateway device database migration upon an upgrade creates
gateway devices objects from references in network gateway
objects.
While these gateway devices are perfectly usable
in network gateways, they are not directly visible to tenants
and also cannot be updated to change details such as name,
connector type or ip as well as the client certificate.

This patch fixes the DB migration in order to ensure tenant
have access to gateway devices created after an upgrade.
This patch also modifies the l2 gateway nsxlib module to
ensure request bodies are correctly created even when not all
the attributes of a gateway device are specified.

Change-Id: I7077e9884adc739fb75e64a6e9a17a124d79fb6b
Closes-Bug: 1293617
Stop removing ip allocations on port delete

The _delete_port() method was manually removing related
IPAllocation instances despite the existence of a perfectly
good cascade deletion relationship in the model.  This patch
puts an end to that nonsense and the potential for deadlock that
it represented.

Closes-bug: #1288379
Related-Bug: #1283522

Change-Id: Ib31550fa9000fc75768a327cb6cc1c419e06568f
Merge "NSX: Ensure gateway devices are usable after upgrade"
Merge "Kill 'Skipping unknown group key: firewall_driver' log trace"
Merge "Stop removing ip allocations on port delete"