zeromq socket pinned to the thread that created it, see #2863
(cherry picked from commit 63f0021ed015eb35153e8a9826d4ddbc8aa96a37)
Merge pull request #1110 from akka/wip-2863-zeromq-pinned-2.1-patriknw

zeromq socket pinned to the thread that created it, see #2863