Sponsored by: Netflix

When a blocking system call is ongoing, the error message shown was
wrong. It was indicated that a blocking system call is on-going when
the program terminates. This is correct, but hides the error message
which describes why packetdrill is terminating.

Sponsored by:	Netflix

FreeBSD supports usleep(), so use it.
Sonsored by Netflix.

This fixes a bug on non-Linux system for the handling of
blocking system calls. While waiting, release the state
mutex.
Sponsored by Netflix.

Only send the cleanup messages when the socket is not in a front state.
This fixes a bug where in case of the SUT being a server was sent
a TCP RST with wildcard addresses and ports.

Current limitations:
* Chunk parameters are not yet supported.
* Error causes are not yet supported.
* Chunks can't be bundled with COOKIE-ECHO chunks.
* Chunk flags are not supported.
* Chunk lengths are not supported.
* Gap reports and duplicate TSNs are not supported for SACK chunks.
* SCTP related ICMP messages are not supported.
This version is only tested in a limited way, only on FreeBSD and
only in local mode.

Initial commit for the packetdrill network stack testing tool:

  https://code.google.com/p/packetdrill/



Signed-off-by: Neal Cardwell <ncardwell@google.com>