Use old atomic memory access APIs to support gcc 4.4.7
Use old atomic memory access APIs to support gcc 4.4.7

The default gcc version in rhel/centos 6.x is 4.4.7, which does not
support
__atomic_load_n() etc atomic functions.
Use __sync_lock_test_and_set() now to make this tool can be compiled on
rhel/centos 6.x, without upgrading the gcc to new versions.

Microsoft/ntttcp-for-linux,Microsoft/ntttcp-for-linux