coll/ucc: Set default mca param value before registration

Setting the default right before registration is the well
known behavior and prevents issues as the pointer can be
set to NULL during param deregistration.

Signed-off-by: William Zhang <wilzhang.amazon.com>

Author: William Zhang

ompi/mca/coll/ucc/coll_ucc_component.c

@@ -91,11 +91,13 @@ static int mca_coll_ucc_register(void)
                                     OPAL_INFO_LVL_3, MCA_BASE_VAR_SCOPE_READONLY,
                                     &cm->runtime_version);
 
+    cm->cls = "";
     mca_base_component_var_register(c, "cls",
                                     "Comma separated list of UCC CLS to be used for team creation",
                                     MCA_BASE_VAR_TYPE_STRING, NULL, 0, 0,
                                     OPAL_INFO_LVL_6, MCA_BASE_VAR_SCOPE_READONLY, &cm->cls);
 
+    cm->cts = COLL_UCC_CTS_STR;
     mca_base_component_var_register(c, "cts",
                                     "Comma separated list of UCC coll types to be enabled",
                                     MCA_BASE_VAR_TYPE_STRING, NULL, 0, 0,