A GROUP BY query which uses "MIN(pk)" and has "pk<>const" in the
WHERE clause would produce wrong result when handled with "Using index
for group-by".  Here "pk" column is the table's primary key.

The problem was introduced by fix for MDEV-23634. It made the range
optimizer to not produce ranges for conditions in form "pk != const".

However, LooseScan code requires that the optimizer is able to
convert the condition on the MIN/MAX column into an equivalent range.
The range is used to locate the row that has the MIN/MAX value.

LooseScan checks this in check_group_min_max_predicates(). This fix
makes the code in that function to take into account that "pk != const"
does not produce a range.