The virSocketParseAddr function was accepting any AF_* constant
and using that to set the ai_flags field in struct addrinfo.
This is invalid, since address families must go in the ai_family
field of the struct.

* src/util/network.c: Fix handling of address family
* src/conf/network_conf.c, src/network/bridge_driver.c: Pass
  AF_UNSPEC instead of relying on it being 0.