latency_probe: display number of reply messages

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
performance: avoid having too many I/O syscalls

Link: https://github.com/GeneAssembly/biosal/issues/789
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
Reviewed-by: George K. Thiruvathukal <gkt@cs.luc.edu>