Add vSphere crawler only to crawl target application

There is no similar ASG concept in vSphere as in AWS and auto grouping all VMs by parrent folder name makes over-chaos to the whole vSphere. Specifying all VMs under the same absolute folder path as a group is a more precise way to inject faulty into target applications. So I add a VsphereChaosCrawler to crawl only VMs under target folder.
Looks like all this logic can be replaced with:

```
if (privateKey == null) {
       privateKey = config.getStrOrElse("simianarmy.chaos.ssh.password", null);
}
if (privateKey != null) {
       this.sshCredentials = LoginCredentials.builder().user(sshUser).privateKey(privateKey).build();
}
```

or am I missing a case ?