sharing: Fix network row visible name bug

(As commented on in !1735 (merged), here's the fix)

In cc_sharing_networks_new_row, the network_name is not being set to the new row, but to self->current_row. This is incorrect behavior, as it leaves the new row without any title, and overwrites the title of the current row incorrectly to the last network entry in the enabled networks list. This fix correctly sets the name to the new row instead.

This problem is at least discussed in #2318 (closed) (point 3) and causes some confusion in #2299 as well.

It originates from f043ca36, before that it was correctly setting the label to row instead of current_row too.

Before (with the title set to the function which calls adw_preferences_row_set_title)

After