test/system: use DISABLE_HC_SYSTEMD for 2 tests

The problem is by default we create the systemd timers and run hc in the
background. This means any tests who depend on exact hc timing can get
broken by this so use the DISABLE_HC_SYSTEMD=true env which makes podman
skip creating the systemd timers but still allows you to manually run
the commands.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>