test: add multi-thread remote free test, which shows contention on remote free list.     - note. meas_barrier cannot called multiple times with different number of cores.       To work around that, always call it twice to recover its internal value to initial value.
test: add multi-thread remote free test, which shows contention on remote free list.
    - note. meas_barrier cannot called multiple times with different number of cores.
      To work around that, always call it twice to recover its internal value to initial value.

gparmer/ps