networkxml2conftest: Don't leak dnsmasq capabilities

networkxml2conftest: Don't leak dnsmasq capabilities

==18324== 32 bytes in 1 blocks are still reachable in loss record 41 of 114
==18324==    at 0x4C2C070: calloc (vg_replace_malloc.c:623)
==18324==    by 0x4EA479B: virAlloc (viralloc.c:144)
==18324==    by 0x4EA674A: virBitmapNewQuiet (virbitmap.c:77)
==18324==    by 0x4EA67F7: virBitmapNew (virbitmap.c:106)
==18324==    by 0x4EC777D: dnsmasqCapsNewEmpty (virdnsmasq.c:801)
==18324==    by 0x4EC781B: dnsmasqCapsNewFromBuffer (virdnsmasq.c:815)
==18324==    by 0x407CF4: mymain (networkxml2conftest.c:99)
==18324==    by 0x409CF0: virTestMain (testutils.c:982)
==18324==    by 0x4080EA: main (networkxml2conftest.c:136)

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