Avoid 1 case of holding a semaphore while mmap callbacks are being made.

Avoid 1 case of holding a semaphore while mmap callbacks are being made.
* runtime/task_finder.c (__stp_call_mmap_callbacks_with_addr): Renamed
  from __stp_call_mmap_callbacks_with_vma().  Also added some code from
  __stp_utrace_task_finder_target_syscall_exit() that locks the 'mmap_sem'
  semaphore.  This avoids holding the semaphore while the mmap callbacks
  are made.
  (__stp_utrace_task_finder_target_syscall_exit): Just calls
  __stp_call_mmap_callbacks_with_addr() in the mmap case.