pulsar-admin source create fails and exist 0 with a wrong source type

**Describe the bug**
The **pulsar-admin source create** fails but exit with 0 when deploying an invalid source type.

**To Reproduce**
```
bin/pulsar-admin source create --source-type xxx
Invalid source type 'xxx' -- Available sources are: [cassandra-source]
...
echo $?
0
```

**Expected behavior**
Failed source deployment should exit with a return code greater than 0

Affected Version: Pulsar 2.8.1

Start with the reproduced bin/pulsar-admin source create --source-type xxx command and trace how the invalid source type result is handled. Locate the source-create entry point and its exit-status path, then verify that the failed deployment returns a nonzero status while successful creation still succeeds.

Written by the indexing model from the issue text.