Running the agent commands twice in a row does not work

Running twice in a row the `agent create image` and `agent create pxe-files`  command does not work.

Always

1. Run `agent create image` command with install-config and agent-config
2. The agent iso is created successfully
3. Again run `agent create image` command with install-config and agent-config

./bin/openshift-install agent create image 
INFO Consuming Install Config from target directory  
INFO Consuming Agent Config from target directory  
FATAL failed to write asset (Agent Installer ISO) to disk: cannot generate ISO image due to configuration errors

The agent iso is created successfully

The steps to reproduce and actual results are same for `agent create pxe-files` command. In case of pxe command, the expected result is 
'INFO PXE-files created in: pxe'