util: Use default group's mask for unspecified resctrl allocations

util: Use default group's mask for unspecified resctrl allocations

Introduce virResctrlAllocCopyMasks() and use that to initially copy the default
group schemata to the allocation before reserving any parts of the cache.  The
reason for this is that when new group is created the schemata will have unknown
data in it.  If there was previously group with the same CLoS ID, it will have
the previous valies, if not it will have all bits set.  And we need to set all
unspecified (in the XML) allocations to the same one as the default group.

Some non-Linux functions now need to be made public due to this change.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1289368

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