perf sort: Use pclose() instead of fclose() on pipe stream

cppcheck message:
[tools/perf/util/sort.c:277]: (error) Mismatching allocation and deallocation: fp

Also fix descriptor leak on error and always initialize the "fp" variable.

Signed-off-by: Thomas Jarosch <thomas.jarosch@intra2net.com>
Link: http://lkml.kernel.org/r/1359112354.yZcisNZ4k0@storm
Link: http://lkml.kernel.org/r/2266358.qvDXKLvJ67@storm


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>