This commit fixes a leak of mmap'ed ring buffer that was not
unmaped when a socket was closed. In addition, the leak could
break an inline channel on certain configurations.
Also slightly changed AFPCreateSocket():
1. If an interface is not up, it does not try to apply any
settings to a socket. This reduces a number of error messages
while an interface is down.
2. Interface is considered active if both IFF_UP and IFF_RUNNING
are present.