I apologise for necoposting such an old topic but I ran into this exact problem recently and all I could find via Googling was "This is what the function does" and nothing related to this problem apart from this post.
I looked at the "fix" and didn't really understand how this fix solved the problem so I experimented and discovered the question marks above my head were well founded.
Yes, the above method DOES indeed fix the problem but it is a fluke. By adding the $$ in front of adminurl he is basically calling an empty string since he is storing the URL inside a variable and then trying to use a variable with a name that matches the url. Since he never created a variable called $"mysite.com/wp-admin" $$adminurl will always return an empty string.
As such I did one final experiment and simply omitted the use of admin_url() completely and that worked perfectly. I.e.
__('WP SMART CRM Documents', 'mytextdomain'),
That is the solution to the double domain issue. Ideally I would also like to have known the answer to the posters question and understand WHY the domain is returned twice but as long as this works, I can live with that.