2-1.13 Small patch.

[beenph]

Soon after 2-1.13 was released we where informed of a small issue with
some output plugins when barnyard2 was exiting or receiving HUP
signal.

This is now fixed in the master and the tag release, build was not
changed either.

People who would upgrade from a previous 2-1.13 binary do not need to
perform any special opertations beside compiling the source an
updating their binaries.

Thanks to Bill Green for reporting the problem initial and C. L.
Martinez who also experienced the same issue.

Cheers and thank you all.
-elz