Make .ajax-users-select dropdown consistent

Merged Winnie Hellmann requested to merge winh-ajax-users-dropdown-ee into master

This is the same as

What does this MR do?

Change (one of) the Select2 Ajax users dropdowns to new style.


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Project members Screen_Shot_2017-08-16_at_14.44.14 Screen_Shot_2017-08-16_at_14.48.28
Group members Screen_Shot_2017-08-16_at_14.45.15 Screen_Shot_2017-08-16_at_14.48.11
Group Admin Area Screen_Shot_2017-08-16_at_14.47.23 Screen_Shot_2017-08-16_at_14.47.45
FogBugz import Screen_Shot_2017-09-05_at_10.59.57 Screen_Shot_2017-09-05_at_10.58.49

What are the relevant issue numbers?,