Merge pull request #7389 from shawnl/warning

tree-wide: adjust fall through comments so that gcc is happy

diff --cc src/core/load-fragment-gperf.gperf.m4
Simple merge

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

diff --cc src/network/networkd-network-gperf.gperf
Simple merge

diff --cc src/shared/machine-image.c
Simple merge