ovs-agent: Ensure integration bridge is created

ovs-agent will fail to launch if integration bridge(br-int by default) is not
existed. To fix this, the agent should check and create the bridge if necessary
during launching.

Closes-Bug: 1328076
Change-Id: Iaa6c4d766ca086deb28c8ef7310dbfdcef2c105f
Imported Translations from Transifex

Change-Id: Ib73d875ad6ed9ce7821a508106ad59f5adf5c343
Merge "Imported Translations from Transifex"
Merge "ovs-agent: Ensure integration bridge is created"