Add method to delete server configuration

Description

Add method which deletes configuration of PXE for given server. Server should be given by server_id. Actually server_id could be MAC or hostname but it could be limited only to hostname. Symbolic link hostname redirect to symbolic link MAC so when hostname is given it is simpler to remove this links.

Proposal

Example curl call to delete host configuration:

curl -X DELETE http://{{ pxe_boot_broker_ip }}:5000/boot_images/{{ hostname_to_delete }}

Method should return:

1. 204 if deleted
2. 404 if resource does not exist

Links / references

API design