Merge pull request #17967 from poettering/connect-user-bus

add support for "systemctl --user --machine=foobar@.host" for connecting to user bus of user "foobar"

diff --cc src/busctl/busctl.c
Simple merge

diff --cc src/journal/sd-journal.c
Simple merge

diff --cc src/libsystemd-network/sd-dhcp-client.c
Simple merge