Share the fixed network for Ironic

When using Ironic, ensure the private Neutron network is shared across
all tenants.  This allows connectivity to the host's TFTP server from
nodes booted accross multiple tenants and more closely resembles the current
real world Ironic PXE+IPMI use cases.

Change-Id: I5d293493bafa37b1796f47aa738cfff2e3be9f59
Install sqlalchemy-migrate from master if requested

Added possibility to install sqlalchemy-migrate from master instead of
pypi packages.

Change-Id: I8af92cbb03609799442b05db9772e3c82b76725b
Remove API_RATE_LIMIT variable since it's wrong anyway

The api_rate_limit config option in nova has defaulted to False since
Havana per commit cfdc59860ef1482e3b064f90f719ec9e484590ce. This change
removes the variable and code that's used to set it in nova.conf since
if we left it in we'd change the default to False to match the code, and
we'd be breaking anyone that is relying on this to be True anyway.

Note that this variable exists in devstack essentially for Tempest so we
can set it in devstack-gate, which is kind of a moot point now given the
code defaults to it anyway.

Change I21dbd72f9959a4e3d62c36831df03b351a51172e removes it from
devstack-gate.

Change-Id: Ib0538bdd23b17e519b9c917018ccc9fa8c6425c5
Merge "Remove API_RATE_LIMIT variable since it's wrong anyway"
Merge "Share the fixed network for Ironic"
Merge "Install sqlalchemy-migrate from master if requested"