This makees much more sense for typical service loads, and can
easily be reverted by `ReadOnly=no`.
Also updates and adds various tests for this.
Signed-off-by: Alexander Larsson <alexl@redhat.com>
This adds the "podman-systemd.unit(5)" manpage that describes
the podman generators from a high level, and all the supported
options.
Signed-off-by: Alexander Larsson <alexl@redhat.com>