mkosi: Install python3-psutil

Required to run systemd-networkd-tests.py. Already a dependency of
systemd-tests on Fedora so we don't add it there as it'll be pulled
in via the prepare script.

mkosi.images/system/mkosi.conf.d/10-arch/mkosi.conf

@@ -38,6 +38,7 @@ Packages=
         polkit
         procps-ng
         psmisc
+        python-psutil
         quota-tools
         sbsigntools
         shadow

mkosi.images/system/mkosi.conf.d/10-debian-ubuntu/mkosi.conf

@@ -61,6 +61,7 @@ Packages=
         policykit-1
         procps
         psmisc
+        python3-psutil
         quota
         sbsigntool
         squashfs-tools

mkosi.images/system/mkosi.conf.d/10-opensuse/mkosi.conf

@@ -56,6 +56,7 @@ Packages=
         procps4
         psmisc
         python3-pefile
+        python3-psutil
         quota
         rpm-build
         rsync