Fixes Hyper-V agent RPC calls for ML2 support

Adds support for the RPC report status in the Hyper-V
agent and plugin.

Fixes bug: #1226654

Change-Id: Ie5eee875afc062c536856589d6a3fd0414190f6d
Fix auto-deletion of ports and subnets in ML2

When a network is deleted, certain ports and any subnets referencing
it are auto-deleted. The implementation of
NeutronDBPluginV2.delete_network() does this at the DB level, so ML2's
mechanism drivers were not being called.

Ml2Plugin.delete_network() is changed to not use the base class's
method, and to auto-delete ports and subnets by calling its own
delete_port() and delete_subnet() methods outside of the
transaction. A loop avoids race conditions with ports or subnets being
asynchronously added to the network.

Closes-Bug: 1230330
Change-Id: Icf21400c9938eec29d70da8497b9ef92642131e2
Merge "Fixes Hyper-V agent RPC calls for ML2 support"
Merge "Fix auto-deletion of ports and subnets in ML2"