nodeCapsInitNUMA: Avoid @cpumap leak

nodeCapsInitNUMA: Avoid @cpumap leak

In case the host has 2 or more NUMA nodes, we fetch CPU map for each
node. However, we need to free the CPU map in between loops:

==29513== 96 (72 direct, 24 indirect) bytes in 3 blocks are definitely lost in loss record 951 of 1,264
==29513==    at 0x4C2A700: calloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==29513==    by 0x52AD24B: virAlloc (viralloc.c:144)
==29513==    by 0x52AF0E6: virBitmapNew (virbitmap.c:78)
==29513==    by 0x52FB720: virNumaGetNodeCPUs (virnuma.c:294)
==29513==    by 0x53C700B: nodeCapsInitNUMA (nodeinfo.c:1886)
==29513==    by 0x11759708: vboxCapsInit (vbox_common.c:398)
==29513==    by 0x11759CC4: vboxConnectOpen (vbox_common.c:514)
==29513==    by 0x53C965F: do_open (libvirt.c:1147)
==29513==    by 0x53C9EBC: virConnectOpen (libvirt.c:1317)
==29513==    by 0x142905: remoteDispatchConnectOpen (remote.c:1215)
==29513==    by 0x126ADF: remoteDispatchConnectOpenHelper (remote_dispatch.h:2346)
==29513==    by 0x5453D21: virNetServerProgramDispatchCall (virnetserverprogram.c:437)

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>