GitLab

Fix several issues in ib loopback benchmark:
* use `--report_gbits` and divide by 8 to get GB/s, previous results are
  MiB/s / 1000
* use the ib_write_bw binary built in third_party instead of system path
* update the metrics name so that different hca indices have same metric

**Description**
Use config `log_raw_data` to control whether log the raw data into file or not. The default value is `no`. We can set it as `yes` for some particular benchmarks to save the raw data into file, such as NCCL/RCCL test.

**Description**
Unify metric names of benchmarks.

**Description**
Remove IB device port info in command to fix bug of IB loopback.

**Major Revision**
- Remove IB device port info in command to fix bug of IB loopback 

**Description**
Add RDMA Loopback performance microbenchmark.

**Major Revision**
- Add microbenchmark, example, test, config for RDMA Loopback