virNWFilterObjListFree: Don't leak nwfilters->objs
    
    When adding a nwfilter onto the list in
    virNWFilterObjListAssignDef() this array is re-allocated to match
    demand for new size. However, it is never freed leading to a
    leak:
    
    ==26535== 136 bytes in 1 blocks are definitely lost in loss record 1,079 of 1,250
    ==26535==    at 0x4C2E2BE: realloc (vg_replace_malloc.c:785)
    ==26535==    by 0x54BA28E: virReallocN (viralloc.c:245)
    ==26535==    by 0x54BA384: virExpandN (viralloc.c:294)
    ==26535==    by 0x54BA657: virInsertElementsN (viralloc.c:436)
    ==26535==    by 0x55DB011: virNWFilterObjListAssignDef (virnwfilterobj.c:362)
    ==26535==    by 0x55DB530: virNWFilterObjListLoadConfig (virnwfilterobj.c:503)
    ==26535==    by 0x55DB635: virNWFilterObjListLoadAllConfigs (virnwfilterobj.c:539)
    ==26535==    by 0x2AC5A28B: nwfilterStateInitialize (nwfilter_driver.c:250)
    ==26535==    by 0x5621C64: virStateInitialize (libvirt.c:770)
    ==26535==    by 0x124379: daemonRunStateInit (libvirtd.c:881)
    ==26535==    by 0x554AC78: virThreadHelper (virthread.c:206)
    ==26535==    by 0x8F5F493: start_thread (in /lib64/libpthread-2.23.so)
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
    Reviewed-by: John Ferlan <jferlan@redhat.com>