Allow restart for oneshot units

Picked up from https://github.com/systemd/systemd/pull/7474 , so
coauthored by @robermorales.

test/TEST-41-ONESHOT-RESTART/Makefile

@@ -0,0 +1,9 @@
+BUILD_DIR=$(shell ../../tools/find-build-dir.sh)
+
+all setup run:
+	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --$@
+
+clean clean-again:
+	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --clean
+
+.PHONY: all setup run clean clean-again

test/TEST-41-ONESHOT-RESTART/test.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+set -e
+TEST_DESCRIPTION="Test oneshot unit restart on failure"
+. $TEST_BASE_DIR/test-functions
+
+test_setup() {
+    create_empty_image_rootdir
+
+    (
+        LOG_LEVEL=5
+        eval $(udevadm info --export --query=env --name=${LOOPDEV}p2)
+
+        setup_basic_environment
+        mask_supporting_services
+
+        # setup the testsuite service
+        cat >$initdir/etc/systemd/system/testsuite.service <<EOF
+[Unit]
+Description=Testsuite service
+
+[Service]
+ExecStart=/testsuite.sh
+Type=oneshot
+EOF
+        cp testsuite.sh $initdir/
+
+        setup_testsuite
+    )
+    setup_nspawn_root
+}
+
+do_test "$@"

test/TEST-41-ONESHOT-RESTART/testsuite.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+set -ex
+set -o pipefail
+
+systemd-analyze log-level debug
+systemd-analyze log-target console
+
+# These three commands should succeed.
+! systemd-run --unit=one -p Type=oneshot -p Restart=on-failure /bin/bash -c "exit 1"
+
+sleep 5
+
+if [[ "$(systemctl show one.service -p NRestarts --value)" -le 0 ]]; then
+  exit 1
+fi
+
+TMP_FILE="/test-41-oneshot-restart-test"
+
+touch $TMP_FILE
+
+! systemd-run --unit=two -p StartLimitBurst=3 -p Type=oneshot -p Restart=on-failure -p ExecStart="/bin/bash -c \"printf a >>  $TMP_FILE\"" /bin/bash -c "exit 1"
+
+sleep 5
+
+if [[ $(cat $TMP_FILE) != "aaa" ]]; then
+  exit 1
+fi
+
+systemd-analyze log-level info
+
+echo OK > /testok
+
+exit 0