automation: cleanup test alpine install

Remove parts of initramfs for the test system (domU, and in few tests
dom0 too) that are not not working and are not really needed in this
simple system.

This makes the test log much lighter on misleading error messages.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>

automation/tests-artifacts/alpine/3.18.dockerfile

@@ -40,7 +40,6 @@ RUN \
   rc-update add udev && \
   rc-update add udev-trigger && \
   rc-update add udev-settle && \
-  rc-update add networking sysinit && \
   rc-update add loopback sysinit && \
   rc-update add bootmisc boot && \
   rc-update add devfs sysinit && \
@@ -48,18 +47,17 @@ RUN \
   rc-update add hostname boot && \
   rc-update add hwclock boot && \
   rc-update add hwdrivers sysinit && \
-  rc-update add killprocs shutdown && \
-  rc-update add modloop sysinit && \
   rc-update add modules boot && \
+  rc-update add killprocs shutdown && \
   rc-update add mount-ro shutdown && \
   rc-update add savecache shutdown && \
-  rc-update add sysctl boot && \
   rc-update add local default && \
   cp -a /sbin/init /init && \
   echo "ttyS0" >> /etc/securetty && \
   echo "hvc0" >> /etc/securetty && \
   echo "ttyS0::respawn:/sbin/getty -L ttyS0 115200 vt100" >> /etc/inittab && \
   echo "hvc0::respawn:/sbin/getty -L hvc0 115200 vt100" >> /etc/inittab && \
+  echo > /etc/modules && \
   passwd -d "root" root && \
   \
   # Create rootfs