Cleanup a variable that isn't used if pmi2 support is available

Refs trac:3683

This commit was SVN r28841.

The following Trac tickets were found above:
  Ticket 3683 --> https://svn.open-mpi.org/trac/ompi/ticket/3683

orte/mca/ess/pmi/ess_pmi_module.c

@@ -79,7 +79,6 @@ orte_ess_base_module_t orte_ess_pmi_module = {
 };
 
 static bool app_init_complete=false;
-static int pmi_maxlen=0;
 
 /****    MODULE FUNCTIONS    ****/
 
@@ -160,6 +159,9 @@ static int rte_init(void)
             goto error;
         }
 #else
+        {
+            int pmi_maxlen;
+
             /* get our PMI id length */
             if (PMI_SUCCESS != (ret = PMI_Get_id_length_max(&pmi_maxlen))) {
                 error = "PMI_Get_id_length_max";
@@ -171,6 +173,7 @@ static int rte_init(void)
                 error = "PMI_Get_kvs_domain_id";
                 goto error;
             }
+        }
 #endif
         /* PMI is very nice to us - the domain id is an integer followed
          * by a '.', followed by essentially a stepid. The first integer