Selector fix for finding map items in widget.

Due to [ARTY failure 04/02/14](https://www.pivotaltracker.com/story/show/68767974).  Two separate causes:

1) The div in the mapping modal can now have the infinite_scroll in its class, when it expects only "selector-list"; this has been adapted to a contains() check instead of an = check. Probably [this commit](https://github.com/reciprocity/ggrc-core/commit/fdc1d12b79fa58cbec9cbfad973bca2c16e9451a).

2) Then, the mapping modal selectors (like `mapping_modal_selector_list_first_object`) are not recognizing the div.tree-title-area as visible if it lacks text, so the selector now looks for the parent div, which works whether or not there is text.

Still a remaining problem when it tries to map, but this should at least fix the current failures.