zfs: Resolve RESOURCE_LEAK
zfs: Resolve RESOURCE_LEAK

Found by my Coverity checker - virCheckFlags call could return -1, but
not virCommandFree(destroy_cmd).

Signed-off-by: John Ferlan <87558058f6f829e5ec976c8ef960720af4ff9c7d@redhat.com>

jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,olafhering/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,datto/libvirt,eskultety/libvirt,datto/libvirt,zippy2/libvirt,taget/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,taget/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,eskultety/libvirt,crobinso/libvirt,zippy2/libvirt,zippy2/libvirt,datto/libvirt,crobinso/libvirt,jardasgit/libvirt,jardasgit/libvirt,taget/libvirt,fabianfreyer/libvirt,olafhering/libvirt,libvirt/libvirt,jfehlig/libvirt,olafhering/libvirt,crobinso/libvirt,datto/libvirt,crobinso/libvirt,jardasgit/libvirt,eskultety/libvirt,zippy2/libvirt,taget/libvirt,andreabolognani/libvirt,libvirt/libvirt,andreabolognani/libvirt,eskultety/libvirt,nertpinx/libvirt,datto/libvirt,nertpinx/libvirt,eskultety/libvirt,jfehlig/libvirt,andreabolognani/libvirt,jardasgit/libvirt,olafhering/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,libvirt/libvirt,libvirt/libvirt,taget/libvirt,nertpinx/libvirt,jfehlig/libvirt,fabianfreyer/libvirt