Fix scheduling if node in more than one partition

I found a bug in cons_res/select_p_select_nodeinfo_set_all.

If a node is part of two (or more) partitions the code will only count the number of cores/cpus in the partition that has the most running jobs on that node.

Patch attached to fix the problem.

I also added an new function to bitstring to count the number of bits in an range (bit_set_count_range) and made a minor improvement of (bit_set_count) while reviewing the range version.

Best regards,
Magnus