osc/pt2pt: Fix PSCW after Fence wrong answer.

* If the user uses PSCW synchronization after a Fence then the previous
   epoch is not reset which can cause the PSCW to transfer data before
   it is ready leading to wrong answers.
 * This commit resets the `eager_send_active` in the start call.

Signed-off-by: Joshua Hursey <jhursey@us.ibm.com>

ompi/mca/osc/pt2pt/osc_pt2pt_active_target.c

@@ -10,7 +10,7 @@
  *                         All rights reserved.
  * Copyright (c) 2007-2016 Los Alamos National Security, LLC.  All rights
  *                         reserved.
- * Copyright (c) 2010      IBM Corporation.  All rights reserved.
+ * Copyright (c) 2010-2016 IBM Corporation.  All rights reserved.
  * Copyright (c) 2012-2013 Sandia National Laboratories.  All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
@@ -227,6 +227,12 @@ int ompi_osc_pt2pt_start (ompi_group_t *group, int assert, ompi_win_t *win)
     /* haven't processed any post messages yet */
     sync->sync_expected = sync->num_peers;
 
+    /* If the previous epoch was from Fence, then eager_send_active is still
+     * set to true at this time, but it shoulnd't be true until we get our
+     * incoming Posts. So reset to 'false' for this new epoch.
+     */
+    sync->eager_send_active = false;
+
     OPAL_OUTPUT_VERBOSE((50, ompi_osc_base_framework.framework_output,
                          "ompi_osc_pt2pt_start entering with group size %d...",
                          sync->num_peers));