Capture network throughput with sar in test_info.sh and fix p95 in output which should be p99

Change-Id: I64f2722436b8a325dadef28b66a44b345508e1c3
Reviewed-on: http://review.couchbase.org/37886
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>
Reviewed-by: Li Yang <lichenyang2@gmail.com>