ipalib: host_del: Extend LDAPDelete's takes_options instead of overriding
The host-del command did not accept --continue option, since the
takes_options was overriden and did not take the options from LDAPDelete.
Fix the behaviour.
https://fedorahosted.org/freeipa/ticket/4473
Reviewed-By: Jan Cholasta <jcholast@redhat.com>