fixed race condition to ensure entrance listeners close properly.
fixed race condition to ensure entrance listeners close properly.

Entrance listeners should be closed when the group is closed and all
currently running processes have already been invoked.

Signed-off-by: Ted Young <66c8979f4bb24f9b49cd80cbed4f06a51450d4f8@pivotallabs.com>

jenspinney/ifrit,lwoydziak/ifrit,jfmyers9/ifrit,tedsuo/ifrit