This tweaks the sysusers.d handling logic so that 'm' entries are
now translated to a series of groupadd + useradd + usermod call.
The last usermod call is the notable change, effectively affecting
the list of secondary groups now.
rhel-only
Resolves: #2217149
There should be almost no functional change, but shellcheck complains
less. User/group descriptions with escaped characters are handled
properly.
rhel-only
Resolves: #2217149
