Move the tunnelled migration unix socket to /var/lib/libvirt/qemu

Since the qemu process is running as qemu:qemu, it can't actually
look at the unix socket in /var/run/libvirt/qemu which is owned by
root and has permission 700.  Move the unix socket to
/var/lib/libvirt/qemu, which is already owned by qemu:qemu.

Thanks to Justin Clift for test this out for me.
Signed-off-by: NChris Lalancette <clalance@redhat.com>

src/qemu/qemu_driver.c

@@ -10482,7 +10482,7 @@ qemudDomainMigratePrepareTunnel(virConnectPtr dconn,
     vm->def->id = -1;
 
     if (virAsprintf(&unixfile, "%s/qemu.tunnelmigrate.dest.%s",
-                    driver->stateDir, vm->def->name) < 0) {
+                    driver->libDir, vm->def->name) < 0) {
         virReportOOMError();
         goto endjob;
     }
@@ -10951,7 +10951,7 @@ static int doTunnelMigrate(virDomainPtr dom,
     /* Stage 1. setup local support infrastructure */
 
     if (virAsprintf(&unixfile, "%s/qemu.tunnelmigrate.src.%s",
-                    driver->stateDir, vm->def->name) < 0) {
+                    driver->libDir, vm->def->name) < 0) {
         virReportOOMError();
         goto cleanup;
     }