detect: Adjusting code semantic
detect: Adjusting code semantic

On commit 8099ef6d43204995c70e23aaa3ecbba570980eff, we are now searching
disks by analyzing slots.

Using disk_num to interate on slots isn't very logical. So let's rename
it to slot_num.

redhat-cip/edeploy,enovance/edeploy,lebauce/edeploy,enovance/edeploy,lebauce/edeploy,redhat-cip/edeploy,enovance/edeploy,redhat-cip/edeploy,lebauce/edeploy,lebauce/edeploy,enovance/edeploy,redhat-cip/edeploy