Fetch routers ports for metadata access from DB

Bug 1176963

There is no need to retrieve the ports from the NVP backend, so
a DB query will be enough.

Change-Id: If3529cc5694434e8cdc9d21a4043f94212146d2d
Improve checking of return values for functions in linuxbridge agent plugin

Fixes bug 1167780

Changed return values for some ensure_* functions to make them more consistent.
Now all ensure_* functions return None on failure and return the entity that was
created within the function when successful. Made changes to the unit tests to
reflect the changed return values.

Change-Id: Ib015ee7cee50bae5d91a4e109e7381519c1e14f7
Log a warning if dnsmasq version is below the minimum required

It has been noted that older versions of dnsmasq may have unexpected
behavior, so this patch introduces a check on dnsmasq version; if
the minimum version is not met, a warning is logged. This is less
invasive than raising an Exception and abort the dhcp agent, even
though this also seems like a perfectly acceptable behavior.

Fixes bug 1170793

Change-Id: Idd91c3753fb05f223ed0e3c53ad692ee65ea4905
in dhcp_agent, always use quantum.conf root_helper

Fixes bug #1178003.

For the most part, the dhcp agent uses the root_helper setting from the [AGENT]
section of /etc/quantum/quantum.conf. However, in a couple of spots, the
root_helper setting from the [DEFAULT] section of /etc/quantum/dhcp_agent.ini
was being used.

Change-Id: Id2f3140374a705cf7a0d2a784e4f321cc54f602e
Imported Translations from Transifex

Change-Id: I7149051e67d4a9e2932b04b066b7e06983a1dde0
Create a common function for method _parse_network_vlan_ranges used
by plugins.

The _parse_network_vlan_ranges method does the same thing for the
linuxbridge, ovs, and hyperv plugins. Create a common function for
the plugins to use instead. This paves the way for improving vlan
range verification (see #1169266) in one place.

Fixes Bug #1177428

Change-Id: Ie8c20807e9146dd9c8bc011dd3a4dc10ec871e0b
Merge "in dhcp_agent, always use quantum.conf root_helper"
Merge "Improve checking of return values for functions in linuxbridge agent plugin"
Merge "Fetch routers ports for metadata access from DB"
Merge "Create a common function for method _parse_network_vlan_ranges used by plugins."
Add kill-metadata rootwrap filter to support RHEL.

 * Fixes bug 1178419

Change-Id: I9c1cf0d19d1134ec3b85c905c6c8bb7145847ce7
Merge "Log a warning if dnsmasq version is below the minimum required"