Incorrect redirection link for mentioned users that has the name 'deadbeef' (BB-16149)

###Summary
When mentions a username which has the word deadbeef such as @deadbeef or @deadbeef<Numbers> or @<Numbers>deadbeef or @dead<Numbers>beef

The mention name instead of redirect to the User Profile, it redirects to https://bitbucket.org/testusername/testrepository/commits/<mentioned_username>

###Steps to Reproduce

1. Go to a commit or Pull Request
2. Click comment
3. Use '@' to mention username with the word 'deadbeef'
4. Click preview

###Expected Results###
The link redirects to https://bitbucket.org/testusername/testrepository/commits/<mentioned_username>

###Actual Results###
The link redirects to https://bitbucket.org/<mentioned_username>

###Notes###
The mentioned name doesn't render the mentioned user full name either.
The comment render and display '@<deadbeef>' instead of '<User Full Name>'