Adds default route to DHCP namespace for upstream name resolution.

Any time the DHCP server is updated this code will maintain a default
route in the DHCP namespace using the gateway_ip attribute of the
first DHCP-enabled IPV4 subnet in the list of subnets where gateway_ip
is not None.  This strategy uses the same gateway ip that the DHCP
server hands to the VMs on the network.

Change-Id: I0807550a848e1b610c7775d215643ad9c83629ed
Fixes: Bug #1181378
Imported Translations from Transifex

Change-Id: I5981d9309ebfec257a82b579828af96c359fb85d
Fix single-version-externally-mananged typo in setup.cfg

Corrects the typo in setup.cfg to use single-version-externally-managed
for pbr.

Fixes bug 1192987

Change-Id: I039b51897ec180148e5095349e4567759f2711a5
Merge "Imported Translations from Transifex"
Merge "Fix single-version-externally-mananged typo in setup.cfg"
Merge "Adds default route to DHCP namespace for upstream name resolution."