cluster/afr: Fix memory leak of file-path in self-heal-daemon

        Backport of http://review.gluster.org/4790

Note: Only the part which fixes the memory leak is backported

shd event has path which needs to be freed as part of circular buffer cleanup.
This patch introduces the functionality so that self-heal-daemon can use it.

Change-Id: I3f3823d5587eda2fcb278f0fdb89123a31c9d786
BUG: 1119894
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/8541
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>