numa: split util/ and conf/ and support non-contiguous nodesets

numa: split util/ and conf/ and support non-contiguous nodesets

This is a reaction to Michal's fix [1] for non-NUMA systems that also
splits out conf/ out of util/ because libvirt_util shouldn't require
libvirt_conf if it is the other way around.  This particular use case
worked, but we're trying to avoid it as mentioned [2], many times.

The only functions from virnuma.c that needed numatune_conf were
virDomainNumatuneNodesetIsAvailable() and virNumaSetupMemoryPolicy().
The first one should be in numatune_conf as it works with
virDomainNumatune, the second one just needs nodeset and mode, both of
which can be passed without the need of numatune_conf.

Apart from fixing that, this patch also fixes recently added
code (between commits d2460f85^..5c8515620) that doesn't support
non-contiguous nodesets.  It uses new function
virNumaNodesetIsAvailable(), which doesn't need a stub as it doesn't use
any libnuma functions, to check if every specified nodeset is available.

[1] https://www.redhat.com/archives/libvir-list/2014-November/msg00118.html
[2] http://www.redhat.com/archives/libvir-list/2011-June/msg01040.html

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>