Bug 1791095

This bug is created as a clone of upstream ticket:
https://pagure.io/389-ds-base/issue/50798

#### Issue Description

When installing FreeIPA server on fedora 31 with the python library, the following message is displayed:
```
...
  [1/44]: creating directory server instance
/usr/lib/python3.7/site-packages/lib389/instance/setup.py:786: BytesWarning: str() on a bytes instance
  self.log.debug(f"CMD: {' '.join(result.args)} ; STDOUT: {result.stdout} ; STDERR: {result.stderr}")
  [2/44]: configure autobind for root
...
```

Uninstallation also produces the same type of message:
```
...
Unconfiguring directory server
/usr/lib/python3.7/site-packages/lib389/instance/remove.py:105: BytesWarning: str() on a bytes instance
  _log.debug(f"CMD: {' '.join(result.args)} ; STDOUT: {result.stdout} ; STDERR: {result.stderr}")
Unconfiguring ipa-custodia

...
```
#### Package Version and Platform
389-ds-base-1.4.2.5-3.fc31.x86_64
freeipa-server-4.9.0.dev201912201432+git-0.fc31.x86_64 (from copr @freeipa/freeipa-master-nightly)

#### Steps to reproduce

1. ipa-server-install --domain $DOMAIN --realm $REALM -a Secret123 -p Secret123 -U
2. ipa-server-install --uninstall -U

### Proposed fix

In the file `lib389/instance/setup.py`, the line 786:
```
            self.log.debug(f"CMD: {' '.join(result.args)} ; STDOUT: {result.stdout} ; STDERR: {result.stderr}")
```
should use `result.stdout.decode('utf-8')` and `result.stderr.decode('utf-8')`

In the file `lib389/instance/remove.py` the line 105:
```
        _log.debug(f"CMD: {' '.join(result.args)} ; STDOUT: {result.stdout.decode()} ; STDERR: {result.stderr.decode()}")
```
should use `result.stdout.decode('utf-8')` and `result.stderr.decode('utf-8')`