Disable mscclpp (#1614)

* disable mscclpp by default

src/init.cc

@@ -114,11 +114,9 @@ bool operator ==(const ncclUniqueId& a, const ncclUniqueId& b) {
 }
 
 RCCL_PARAM(MscclppThreshold, "MSCCLPP_THRESHOLD", (size_t)(1024*1024));
-static constexpr int64_t defaultEnableMscclpp = 1;
-#else
-static constexpr int64_t defaultEnableMscclpp = 0;
 #endif
 
+static constexpr int64_t defaultEnableMscclpp = 0;
 RCCL_PARAM(MscclppEnabled, "MSCCLPP_ENABLE", defaultEnableMscclpp);
 RCCL_PARAM(MscclppForceEnabled, "MSCCLPP_FORCE_ENABLE", 0);