Update our usage of ebtables to pass the --concurrent flag.
With --concurrent ebtables will attempt to acquire a lock file
before making changes. This allows multiple processes, such as
nova an libvirt, to safely access ebtables at the same time.
Support for using --concurrent was added in libvirt 1.2.11, since
we don't know the version of libvirt being used in all
deployments we still retry the ebtables call several times just
in case libvirt isn't using --concurrent.
DocImpact:
* nova now requires ebtables 2.0.10 or later
* nova now recommends libvirt 1.2.11 or later
Change-Id: I00ff805cee9653508f013f8aa6d206362ac0f6cb
Partial-Bug: #1501366
Chet Burgess
103cb6bdc3