When creating/deleting lbaas objects at a high rate (like tempest api tests do)
deploy/undeploy_unstance methods of haproxy namespace driver
may be executed concurrently which leads to different conflicts with
network namespaces and interfaces created by the diver.
@synchronized decorator should be used in order to ensure that only one thread
will execute one of the methods at a time.
Closes-Bug: #1260692
Change-Id: Ibe86653c20c9a4e0b4e7b3b2cefbd445428b82da
082d80681c