iperf3 client does NOT report cpu_utilization_percent to server

# Context

* Version of iperf3: latest master

* Hardware: VirtualBox VM

* Operating system (and distribution, if any): CentOS release 6.4 (Final)

* Other relevant information (for example, non-default compilers,
libraries, cross-compiling, etc.): Static native build (./configure --enable-static --disable-shared)

# Bug Report

* Expected Behavior: Both client and server JSON have both client and server cpu_utilization_percent

* Actual Behavior: Client JSON contains both host and remote cpu_utilization_percent (working correctly). Server JSON only contains host cpu_utilization_percent (remote is all zeros).

* Steps to Reproduce - Client: ./iperf3 -c localhost -t 1 --json > /tmp/iperfc.master.json
```
# cat /tmp/iperfc.master.json | grep 'cpu_util' -A 7
"cpu_utilization_percent": {
"host_total": 32.868187611614886,
"host_user": 5.842320347964546,
"host_system": 28.025060167043431,
"remote_total": 20.288637666431178,
"remote_user": 3.1487965658301182,
"remote_system": 17.439537588637879
}
```
* Steps to Reproduce - Server: ./iperf3 -s -1 --json > /tmp/iperfs.master.json
```
# cat /tmp/iperfs.master.json | grep 'cpu_util' -A 7
"cpu_utilization_percent": {
"host_total": 20.288637666431178,
"host_user": 3.1487965658301182,
"host_system": 17.439537588637879,
"remote_total": 0,
"remote_user": 0,
"remote_system": 0
}
```

* Possible Solution: Add cpu_utilization_percent from client in server JSON output.