Add Management Network For System Administration.

Add Management Network For System Administration.

This change adds a system management network to all overcloud
nodes. The purpose of this network is for system administration,
for access to infrastructure services like DNS or NTP, or for
monitoring. This allows the management network to be placed on a
bond for redundancy, or for the system management network to be
an out-of-band network with no routing in or out. The management
network might also be configured as a default route instead of the
provisioning 'ctlplane' network.

This change does not enable the management network by default. An
environment file named network-management.yaml may be included to
enable the network and ports for each role. The included NIC config
templates have been updated with a block that may be uncommented
when the management network is enabled.

This change also contains some minor cleanup to the NIC templates,
particularly the multiple nic templates.

Change-Id: I0813a13f60a4f797be04b34258a2cffa9ea7e84f