NSX: fix validation logic on network gateway connect

This patch adds validation for the segmentation ID when the
network type for the gateway connection is vlan.
This will avoid requests with invalid vlan IDs are sent to
the backend resulting in 500 error responses being
returned to API users.

To this aim this patch slightly alters the current validation
logic due to the fact that some checks are unnecessary since
the same routine sets default values which avoid the
conditions being checked.

Change-Id: If0e71f6fdf27a49f0eda727e21405cffbc260a7a
Closes-Bug: #1340431
The default value of quota_firewall_rule should not be -1

A bad tenant User can create unlimited firewall rules to
"attack" the network node, so I modify the default value to 100.

Change-Id: I485c24cb1a7ed77dee81356fe6d95276808a47d4
Closes-Bug: #1346372
NSX: fix router ports port_security_enabled=False

Previously there was a bug that resulted in a security group being
added to router ports which was not supported in NSX. Removing the
security group didn't actually completely solve the problem as we
never cleared the allowed_address_pairs on the router port. This
patch fixes this issue by disabling port_security_enabled on the
router port.

Change-Id: Ib61756e3bd5866318cbc3bb9856344571399d656
Closes-bug: 1344266
Related-bug: 1329043
Merge "NSX: fix validation logic on network gateway connect"
Merge "NSX: fix router ports port_security_enabled=False"
Merge "The default value of quota_firewall_rule should not be -1"