Correct bad parameter names.

We were using MPIR_PARAM_NEMESIS_ENABLE_CKPOINT in some cases and
MPIR_PARAM_ENABLE_CKPOINT in some cases.  This patch makes the names
consistent.
Signed-off-by: Ken Raffenetti <raffenet@mcs.anl.gov>

src/mpid/ch3/channels/nemesis/src/ch3_progress.c

@@ -310,7 +310,7 @@ int MPIDI_CH3I_Progress (MPID_Progress_state *progress_state, int is_blocking)
     }
     
 #ifdef ENABLE_CHECKPOINTING
-    if (MPIR_PARAM_ENABLE_CKPOINT) {
+    if (MPIR_PARAM_NEMESIS_ENABLE_CKPOINT) {
         if (MPIDI_nem_ckpt_start_checkpoint) {
             MPIDI_nem_ckpt_start_checkpoint = FALSE;
             mpi_errno = MPIDI_nem_ckpt_start();

src/mpid/ch3/channels/nemesis/src/mpid_nem_ckpt.c

@@ -146,7 +146,7 @@ int MPIDI_nem_ckpt_init(void)
 
     MPIDI_FUNC_ENTER(MPID_STATE_MPIDI_NEM_CKPT_INIT);
 
-    if (!MPIR_PARAM_ENABLE_CKPOINT)
+    if (!MPIR_PARAM_NEMESIS_ENABLE_CKPOINT)
         goto fn_exit;
     
     client_id = cr_init();

src/pm/hydra/ui/mpich/utils.c

@@ -1742,7 +1742,7 @@ HYD_status HYD_uii_mpx_get_parameters(char **t_argv)
     /* If the user set the checkpoint prefix, set env var to enable
      * checkpointing on the processes  */
     if (HYD_server_info.user_global.ckpoint_prefix)
-        HYDU_append_env_to_list("MPIR_PARAM_ENABLE_CKPOINT", "1",
+        HYDU_append_env_to_list("MPIR_PARAM_NEMESIS_ENABLE_CKPOINT", "1",
                                 &HYD_server_info.user_global.global_env.system);
 
     /* Preset common environment options for disabling STDIO buffering