pcp-atop: ensure allocated task memory is always initialised
pcp-atop: ensure allocated task memory is always initialised

We've received a report from a customer and intermittent failures
in test qa/1080 from valgrind, along these lines:

Invalid read of size 8
at 0x4248A1: compcpu (showlinux.c:2031)
by 0x4B38E74: msort_with_tmp.part.0 (in /usr/lib64/libc-2.30.so)
by 0x4B38E01: msort_with_tmp.part.0 (in /usr/lib64/libc-2.30.so)
by 0x4B38E01: msort_with_tmp.part.0 (in /usr/lib64/libc-2.30.so)
by 0x4B38E01: msort_with_tmp.part.0 (in /usr/lib64/libc-2.30.so)
by 0x4B38E01: msort_with_tmp.part.0 (in /usr/lib64/libc-2.30.so)
by 0x4B38E01: msort_with_tmp.part.0 (in /usr/lib64/libc-2.30.so)
by 0x4B38E01: msort_with_tmp.part.0 (in /usr/lib64/libc-2.30.so)
by 0x4B39345: qsort_r (in /usr/lib64/libc-2.30.so)
by 0x41CA8A: generic_samp (showgeneric.c:645)
by 0x4043E7: engine (atop.c:686)
by 0x403F07: main (atop.c:478)
Address 0x188 is not stack'd, malloc'd or (recently) free'd

I've found a couple of places where we might read uninitialized
memory after a malloc - closed those holes, and now running the
test in a loop 250 times, I've not observed the issue anymore.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp