report both local and remote bandwidth in JSON output

[snowdrop4]

Changes

• Add "results_local" and "results_remote" keys to the JSON when --bidirectional and --report-both are turned on
  • This is in addition to the already-existing "results" key when either of those flags are turned off.
  • These key names mimic the output to STDOUT when --bidirectional and --report-both are turned on
• Fix bug where different JSONs were being written and rewritten to the same path, up to three times
  • If --bidirectional and --report-both are both given, then print_full_bw_report() was being called three times, and each time it would write out the JSON
  • This means that: first it would write a JSON with the combined results, then it would write a JSON with the local results, then it would write a JSON with the remote results, and you'd be left only with the remote results, because it would overwrite itself each time (with no indication that this happened)
• Refactor the code a bit to make this all possible:
  • Make a dedicated function for writing out the bandwidth JSON, so we can avoid calling it three times
  • Make a helper function for summing two bandwidth reports, for reporting the aggregate results

---

Example

ib_send_bw --bidirectional --report_gbits --report-both --size=8388608

{
"test_info": {
"test": "Send_Bidirectional_BW_Test",
"Dual_port": "OFF",
"Device": "mlx5_0",
"Number_of_qps": 1,
"Transport_type": "IB",
"Connection_type": "RC",
"Using_SRQ": "OFF",
"PCIe_relax_order": "ON",
"ibv_wr_API": "ON",
"TX_depth": 128,
"RX_depth": 512,
"CQ_Moderation": 1,
"Mtu": 4096,
"Link_type": "IB",
"Max_inline_data": 0,
"rdma_cm_QPs": "OFF",
"Use_ROCm_memory": "OFF",
"Data_ex_method": "Ethernet"
},
"results": {
"MsgSize": 8388608,
"n_iterations": 1000,
"BW_peak": 709.85,
"BW_average": 674.06,
"MsgRate": 0.010044
},
"results_local": {
"MsgSize": 8388608,
"n_iterations": 1000,
"BW_peak": 346.67,
"BW_average": 331.96,
"MsgRate": 0.004947
},
"results_remote": {
"MsgSize": 8388608,
"n_iterations": 1000,
"BW_peak": 363.18,
"BW_average": 342.10,
"MsgRate": 0.005098
}
}