TEST-55-OOMD: use swap file instead of partition

The partition seems not to work on Ubuntu for some reason, use a
swap file instead

test/TEST-55-OOMD/test.sh

@@ -5,20 +5,19 @@ set -e
 TEST_DESCRIPTION="systemd-oomd Memory Pressure Test"
 IMAGE_NAME="oomd"
 
+# Need to set up swap
+TEST_NO_NSPAWN=1
+
 # shellcheck source=test/test-functions
 . "${TEST_BASE_DIR:?}/test-functions"
 
 test_append_files() {
-    # Create a swap device
+    # Create a swap file
     (
-        mkswap "${LOOPDEV:?}p2"
-        image_install swapon swapoff
+        image_install mkswap swapon swapoff stress
 
-        inst_binary stress
-
-        cat >>"${initdir:?}/etc/fstab" <<EOF
-UUID=$(blkid -o value -s UUID "${LOOPDEV}p2")    none    swap    defaults 0 0
-EOF
+        dd if=/dev/zero of="${initdir:?}/swapfile" bs=1M count=48
+        chmod 0600 "${initdir:?}/swapfile"
 
         mkdir -p "${initdir:?}/etc/systemd/system/init.scope.d/"
         cat >>"${initdir:?}/etc/systemd/system/init.scope.d/test-55-oomd.conf" <<EOF

test/units/testsuite-55.sh

@@ -24,6 +24,13 @@ fi
 
 rm -rf /run/systemd/system/testsuite-55-testbloat.service.d
 
+# Activate swap file if we are in a VM
+if systemd-detect-virt --vm --quiet; then
+    mkswap /swapfile
+    swapon /swapfile
+    swapon --show
+fi
+
 # Configure oomd explicitly to avoid conflicts with distro dropins
 mkdir -p /run/systemd/oomd.conf.d/
 cat >/run/systemd/oomd.conf.d/99-oomd-test.conf <<EOF