Use the total # of processors instead of # online.

Use the total number of processors in the system since the number online can change from time to time.

When running this on a Jetson TX-2 which can bring processors online and offline and running a program under valgrind, these errors are reported:

==4895== Invalid read of size 8
==4895==    at 0x13BA8BC: grpc_completion_queue_create_internal(grpc_cq_completion_type, grpc_cq_polling_type) (completion_queue.cc:440)
==4895==    by 0x13B9B53: grpc_completion_queue_create (completion_queue_factory.cc:76)
==4895==    by 0x1203993: CompletionQueue (completion_queue.h:240)
==4895==    by 0x1203993: ServerCompletionQueue (completion_queue.h:378)
==4895==    by 0x1203993: grpc::ServerBuilder::BuildAndStart() (server_builder.cc:258)
==4895==  Address 0x269c9490 is 16 bytes after a block of size 29,952 alloc'd
==4895==    at 0x7900C3C: calloc (vg_replace_malloc.c:711)
==4895==    by 0x13E50DB: gpr_zalloc (alloc.cc:67)
==4895==    by 0x13CB1D3: grpc_stats_init() (stats.cc:36)
==4895==    by 0x1374C07: grpc_init (init.cc:127)
==4895==    by 0x1203947: GrpcLibraryCodegen (grpc_library.h:45)
==4895==    by 0x1203947: CompletionQueue (completion_queue.h:236)
==4895==    by 0x1203947: ServerCompletionQueue (completion_queue.h:378)
==4895==    by 0x1203947: grpc::ServerBuilder::BuildAndStart() (server_builder.cc:258)
==4895== 
==4895== Invalid write of size 8
==4895==    at 0x13BA8C4: grpc_completion_queue_create_internal(grpc_cq_completion_type, grpc_cq_polling_type) (completion_queue.cc:440)
==4895==    by 0x13B9B53: grpc_completion_queue_create (completion_queue_factory.cc:76)
==4895==    by 0x1203993: CompletionQueue (completion_queue.h:240)
==4895==    by 0x1203993: ServerCompletionQueue (completion_queue.h:378)
==4895==    by 0x1203993: grpc::ServerBuilder::BuildAndStart() (server_builder.cc:258)
==4895==  Address 0x269c9490 is 16 bytes after a block of size 29,952 alloc'd
==4895==    at 0x7900C3C: calloc (vg_replace_malloc.c:711)
==4895==    by 0x13E50DB: gpr_zalloc (alloc.cc:67)
==4895==    by 0x13CB1D3: grpc_stats_init() (stats.cc:36)
==4895==    by 0x1374C07: grpc_init (init.cc:127)
==4895==    by 0x1203947: GrpcLibraryCodegen (grpc_library.h:45)
==4895==    by 0x1203947: CompletionQueue (completion_queue.h:236)
==4895==    by 0x1203947: ServerCompletionQueue (completion_queue.h:378)
==4895==    by 0x1203947: grpc::ServerBuilder::BuildAndStart() (server_builder.cc:258)

After this change, the errors are gone.  We also had many crashes on startup that was likely caused by this problem.

The Jetson has a user-level program that allows a user to changes CPUs to online or offline.  So using the max # possible should reduce potentials for errors like these and at worse over-allocate just a few extra bytes.

src/core/lib/gpr/cpu_linux.cc

@@ -45,7 +45,7 @@ static void init_num_cpus() {
 #endif
   /* This must be signed. sysconf returns -1 when the number cannot be
      determined */
-  ncpus = static_cast<int>(sysconf(_SC_NPROCESSORS_ONLN));
+  ncpus = static_cast<int>(sysconf(_SC_NPROCESSORS_CONF));
   if (ncpus < 1) {
     gpr_log(GPR_ERROR, "Cannot determine number of CPUs: assuming 1");
     ncpus = 1;