Merge pull request #13439 from yuwata/core-support-systemctl-clean-more

core: support systemctl clean more

diff --cc src/core/mount.c
Simple merge

diff --cc src/core/service.c
Simple merge

diff --cc src/core/socket.c
Simple merge

diff --cc src/core/swap.c
Simple merge

diff --cc src/core/unit.c
Simple merge

diff --cc src/core/unit.h
Simple merge