conf: Add the cpu duplicate use check for vm numa settings

conf: Add the cpu duplicate use check for vm numa settings

https://bugzilla.redhat.com/show_bug.cgi?id=1176020

We had a check for the vcpu count total number in <numa>
before, however this check is not good enough. There are
some examples:

1. one of cpu id is out of maxvcpus, can set success(cpu count = 5 < 10):

<vcpu placement='static'>10</vcpu>
<cell id='0' cpus='0-3,100' memory='512000' unit='KiB'/>

2. use the same cpu in 2 cell, can set success(cpu count = 8 < 10):
<vcpu placement='static'>10</vcpu>
<cell id='0' cpus='0-3' memory='512000' unit='KiB'/>
<cell id='1' cpus='0-3' memory='512000' unit='KiB'/>

3. use the same cpu in 2 cell, cannot set success(cpu count = 11 > 10):
<vcpu placement='static'>10</vcpu>
<cell id='0' cpus='0-6' memory='512000' unit='KiB'/>
<cell id='1' cpus='0-3' memory='512000' unit='KiB'/>

Add a check for numa cpus, check if duplicate use one cpu in more
than one cell.

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