virpcitest: Fix variable arguments using in pci_driver_new

In the pci_driver_new function it is possible to set a list of
<vendor:device> IDs that the driver knows. These IDs are passed as
variable arguments and are processed  the usual way using va_start() and
va_arg(). However, after all arguments has been processed, we should
call va_end() what we aren't currently doing.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

tests/virpcimock.c

@@ -405,6 +405,8 @@ pci_driver_new(const char *name, ...)
         driver->len++;
     }
 
+    va_end(args);
+
     make_file(driverpath, "bind", NULL);
     make_file(driverpath, "unbind", NULL);
     make_file(driverpath, "new_id", NULL);