In 8278b763 the default behaviour of annotation
has changes, which was causing a lot of noise in diffs. We decided in #17382
that it is better to get rid of the whole annotate gem, and instead let people
look at schema.rb for the columns in a table.

Fixes: #17382

Previously it was "user has already been taken", when really we were
saying the user has already been reported.

This is intended to prevent the user from creating new objects while the
transaction that removes them is being run, resulting in objects with
nil authors which can then not be edited.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/7117

Tell, Don't Ask.

This simplifies the "Report button" to not use open a dropdown and
adds a tooltip on this button.
This also removes an extra spec and adds missing specs.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>