Fixes #19436 - Better controller selection on host dropdown (#4498)

Always setting to `host` unless the controller is `hostgroup` broke
discovery's usage of the form as it uses the `discoverd_host`
controller.
This reverts the change from `method_path` to `host_or_hostgroup_path`
from commit 637da2f28accc1378f0326d97adcbb2efc5d9808 and moves the
controller correction into `method_path`.