Trying to set up Email pulse adds person twice

[camsaul]

This is on master.

I went to try to create an Email pulse and I used auto-complete to add myself

When I click my name once I get added twice

And when I try to delete one of them I deletes both

I think a reasonable person would expect clicking one user only adds them once, and that adding duplicates is disallowed.

[mazameli]

I also wrote up in #6202 that hitting return/or enter in the autocomplete dropdown doesn't do anything.