Fix sqlalchemy DateTime type usage

In migration f9263d6df56_remove_dhcp_lease there is mistake in
DateTime type usage for mysql, used sa.DATETIME() instead of
sa.DateTime()

Closes-Bug: #1250405

Change-Id: I41fcd3babc64e3307895a92f03c7417577fa7b1d
Fix OVS agent reclaims local VLAN

If a port disappears on an OVS agent, the port is removed of the lvm
vif_ports list. And if it's the last port of the network on this agent,
the network local VLAN is reclaim.

Change-Id: I07e03107eb86a84eeb8e4d06f27a1d2fbd7cea57
Closes-Bug: #1252284
Merge "Fix OVS agent reclaims local VLAN"
Merge "Fix sqlalchemy DateTime type usage"