BUG/MEDIUM: threads: Fix binding thread on bind.

BUG/MEDIUM: threads: Fix binding thread on bind.

The code to parse the "thread" keyword on bind lines was changed to
check if the thread numbers were correct against the value provided with
max-threads-per-group, if any were provided, however, at the time those
thread keywords have been set, it may not yet have been set, and that
breaks the feature, so revert to check against MAX_THREADS_PER_GROUP instead,
it should have no major impact.