units: restore RemainAfterExit=yes in systemd-vconsole-setup.service

units: restore RemainAfterExit=yes in systemd-vconsole-setup.service

This reverts the second part of 8125e8d38e3aa099c7dce8b0161997b8842aebdc.
The first part was reverted in 750e550eba362096d56a35104c6a32631aa67b8e.
The problem starts when s-v-s.s is pulled in by something that is then pulled
in by sysinit.target. Every time a unit is started, systemd recursively checks
all dependencies, and since sysinit.target is pull in by almost anything, we'll
start s-v-s.s over and over. In particular, plymouth-start.service currently
has Wants=s-v-s.s and After=s-v-s.s.