ps: fix cpu utilization sorting

ps: fix cpu utilization sorting

The sniplet below resulted not to be sorted correctly.

for i in $(seq 1 50); do ls -R /usr &>/dev/null 2>&1 & done
    sleep 1; ps -e --sort=pcpu -o pcpu,comm=; pkill ls

Issue is present since older versions of procps (3.2.7/3.2.8).

Reference: http://www.freelists.org/post/procps/top-incorrect-sort,2
Reported-by: Jaromir Capik <jcapik@redhat.com>
Backported-by: Sami Kerola <kerolasa@iki.fi>