Initialize alloc_fns with 0s

Change: 150117973

tensorflow/core/distributed_runtime/rpc/grpc_server_lib.cc

@@ -15,6 +15,7 @@ limitations under the License.
 
 #include "tensorflow/core/distributed_runtime/rpc/grpc_server_lib.h"
 
+#include <cstring>
 #include <limits>
 #include <memory>
 
@@ -330,6 +331,7 @@ class GrpcServerRegistrar {
  public:
   GrpcServerRegistrar() {
     gpr_allocation_functions alloc_fns;
+    memset(&alloc_fns, 0, sizeof(alloc_fns));
     alloc_fns.malloc_fn = port::Malloc;
     alloc_fns.realloc_fn = port::Realloc;
     alloc_fns.free_fn = port::Free;