Networks are not scheduled to DHCP agents for Cisco N1KV plugin

With the config option 'network_auto_schedule = False' in
neutron.conf, networks do not get scheduled to available DHCP
agents. The fix is to explicitly schedule the network as part
of the subnet creation flow.

Conflicts:
	neutron/tests/unit/cisco/n1kv/test_n1kv_plugin.py

Change-Id: Id1f94a5844111a916f984d6dd7bda2cb4e11e1ee
Closes-Bug: #1356609
(cherry picked from commit 0fcedae747f257e2424b669ec65f32b76f12155a)
Merge "Networks are not scheduled to DHCP agents for Cisco N1KV plugin" into stable/icehouse