Fix parse_targeted_inventory to call inv.parse

[agrare]

Instead of calling inventory.inventory_collections and return an array
of inventory collections, convention is to call inventory.parse and
return a persister which is handled easier by the subsequent
save_inventory method.

[miq-bot]

Checked commit agrare@b6521d7 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
1 file checked, 0 offenses detected
Everything looks fine. 🍰