[HAMMER] Add a tool to purge archived storages

[agrare]

Backport of #18902 to replace optimist with trollop

Storages that aren't connected to any hosts aren't automatically deleted
and thus a tool is needed to clean them up.

This looks for storages which aren't represented in the host_storages
table which means they aren't a part of any EMS and can be removed.

>> Storage.create!(:name => "my storage")
>> Storage.create!(:name => "my other storage")

$ tools/purge_archived_storages.rb
* This is a dry run and will not modify the database
* To actually delete archived datastores pass --no-dry-run

Deleting the following storages:
ID [11] Name [my storage]
ID [12] Name [my other storage]

$ tools/purge_archived_storages.rb --no-dry-run
Deleting the following storages:
ID [11] Name [my storage]
ID [12] Name [my other storage]

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1723832

[gtanzillo]

LGTM, just the comment about Trollop

[gtanzillo]

Not sure how important this is but we should probably be using Optimist here instead of Trollop

[agrare]

Actually using trollop was the purpose here since hammer branch doesn't have optimist. #18902 (comment)