"x threads didn't exit" today after my merge); the main() thread
was calling my_init() and my_thread_global_init() which is redudant;
it was not calling my_end() though it's needed.


unittest/mysys/mf_pagecache_consist.c:
  program already calls my_init(), which calls my_thread_global_init(),
  so no need for my_thread_global_init() (double call caused the main()
  thread to wait for itself thus timing out and printing
  "x threads didn't exit".
  my_thread_global_end() is not enough, as we call my_init() we must call
  my_end() (which calls my_thread_global_end()).
unittest/mysys/mf_pagecache_single.c:
  program already calls my_init(), which calls my_thread_global_init(),
  so no need for my_thread_global_init() (double call caused the main()
  thread to wait for itself thus timing out and printing
  "x threads didn't exit".
  my_thread_global_end() is not enough, as we call my_init() we must call
  my_end() (which calls my_thread_global_end()).