Connection closed with RX socket error 9

[mdavidsaver]

@hhslepicka reports a side-effect of #144 in the form of Connection closed with RX socket error 9. Error 9 is EBADF, which previously was treated the same as normal connection end. So it looks like there is a race during TCP connection shutdown. This has potentially nasty consequences as FDs can be reused quickly.

pvAccessCPP/src/remote/codec.cpp

Lines 1343 to 1346 in 3a8a24d

	} else {
	// some other (fatal) error
	errlogPrintf("%s : Connection closed with RX socket error %d\n", _socketName.c_str(), err);
	return -1;

[mdavidsaver]

The results of epics-base/epics-base#30 suggest that an interrupted recv() should return 0. However, given that a interrupted recvfrom() can return EBADF it isn't certain that there is an actual race here.

[mdavidsaver]

While not a fix, a22f866 should hide this message if it occurs during connection shutdown. It appears that some interrupted calls on OSX return EBADF (which I guess is true after close()).