Fix properties search icon and failing spec

Fixes a failing feature spec (Unable to find css ".fa-search")
introduced in 2e9002a36b24b22f120bf9494b51a0fec3eebf4c.

Using the correct icon for the search button fixes this.
Simplify records created form line_item factory

Instead of creating a variant, which creates a product and a master
variant (thus creating two variants), just use the product factory and
reference variant created.

This makes core specs run very slightly faster on my machine (a few
seconds off of ~1:30) and I think this is closer to what people would
expect create(:line_item) to do.

Fixes #4852