Remove extra sleep in exclusive lease helper

What does this MR do?

This MR fixes #216050 (closed), by re-writing the loop logic so that the loop is basically:

until held?
  raise if too_many_attempts?
  sleep unless first_attempt?

  try_obtain
end

The subtle complexities of the loop logic and the attempt to code this as a concise count-down led to the intial problems in managing state.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

/copy_metadata #216050 (closed)