Fixed LP BUG#714808 Assertion `outer_lookup_keys <= outer_record_count'

Analysis:

The function best_access_path() computes the number or records as
follows:

...
      if (rec < MATCHING_ROWS_IN_OTHER_TABLE)
        rec= MATCHING_ROWS_IN_OTHER_TABLE; // Fix for small tables
...
              if (table->quick_keys.is_set(key))
                records= (double) table->quick_rows[key];
              else
              {
                /* quick_range couldn't use key! */
                records= (double) s->records/rec;
              }

Above MATCHING_ROWS_IN_OTHER_TABLE == 10, and s->records == 1,
thus we get an estimated 0.1 records. As a result JOIN::get_partial_join_cost()
for the outer query computes outer_record_count == 0.1 records, which is
meaningless in this context.

Solution:
Round row count estimates that are < 1 to 1.