Update vlog_is_on.cc

SetVLOGLevel locks vmodule_lock however RAW_VLOG at the end also implicitly locks it via InitVLOG3__.

This causes deadlock/segfault.

src/vlog_is_on.cc

@@ -162,6 +162,7 @@ int SetVLOGLevel(const char* module_pattern, int log_level) {
   int result = FLAGS_v;
   int const pattern_len = strlen(module_pattern);
   bool found = false;
+  {
     MutexLock l(&vmodule_lock);  // protect whole read-modify-write
     for (const VModuleInfo* info = vmodule_list;
          info != NULL; info = info->next) {
@@ -186,6 +187,7 @@ int SetVLOGLevel(const char* module_pattern, int log_level) {
       info->next = vmodule_list;
       vmodule_list = info;
     }
+  }
   RAW_VLOG(1, "Set VLOG level for \"%s\" to %d", module_pattern, log_level);
   return result;
 }