mtl/ofi: Change default provider selection behavior.

As more providers get added to libfabric, the default exclude list would need
to be updated.
Instead, we choose to include only the providers known to work by default.

New default:
  - include: psm,psm2,gni
  - exclude: none

(cherry-picked from open-mpi/ompi@e7d46b9)

Author: yburette

ompi/mca/mtl/ofi/mtl_ofi_component.c

@@ -64,16 +64,16 @@ ompi_mtl_ofi_component_register(void)
                                     MCA_BASE_VAR_SCOPE_READONLY,
                                     &param_priority);
 
-    prov_include = NULL;
+    prov_include = "psm,psm2,gni";
     mca_base_component_var_register(&mca_mtl_ofi_component.super.mtl_version,
                                     "provider_include",
-                                    "Comma-delimited list of OFI providers that are considered for use (e.g., \"psm,sockets\"; an empty value means that all providers will be considered). Mutually exclusive with mtl_ofi_provider_exclude.",
+                                    "Comma-delimited list of OFI providers that are considered for use (e.g., \"psm,psm2\"; an empty value means that all providers will be considered). Mutually exclusive with mtl_ofi_provider_exclude.",
                                     MCA_BASE_VAR_TYPE_STRING, NULL, 0, 0,
                                     OPAL_INFO_LVL_1,
                                     MCA_BASE_VAR_SCOPE_READONLY,
                                     &prov_include);
 
-    prov_exclude = "sockets,mxm";
+    prov_exclude = NULL;
     mca_base_component_var_register(&mca_mtl_ofi_component.super.mtl_version,
                                     "provider_exclude",
                                     "Comma-delimited list of OFI providers that are not considered for use (default: \"sockets,mxm\"; empty value means that all providers will be considered). Mutually exclusive with mtl_ofi_provider_include.",