qemu: Add support for resctrl

qemu: Add support for resctrl

We've been building up to this.  This adds support for cputune/cachetune
settings for domains in the QEMU driver.  The addition into
qemuProcessSetupVcpu() automatically adds support for hotplug.  For hot-unplug
we need to remove the allocation only if all the vCPUs were unplugged.  But
since the threads are left running, we can't really do much about it now.

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

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