Description of problem:

Some 3rd party legacy applications or home made scripts are still present and not yet ported to systemd units. If a customer did not embrace NetworkManager for network startup in rhel7, the adoption of RHEL8 is a massive change, and this has impacts also on the daemons startup.

Version-Release number of selected component (if applicable):
systemd-239-31.el8_2.2.x86_64

How reproducible:
Always

Steps to Reproduce:
1. have in rc-local a daemon that need to connect to the network or to bind to a specific ip
2. the rc-local unit is started when network.target is reached, but that does not ensure there's already a network connection or the desired ip (dhcp...)

Actual results:
if something in rc-local need to access the internet, or to bind to an ip not yet available, it will fail.

Expected results:
By ensuring rc-local is started after network-online.target is reached, we can prevent an entire set of failure for those customers who may be force to still use rc-local and not modern application, due to 3rd party vendors not reactive or not avail anymore (think about propietary apps not supported anymore) or internal lack of resources, while reducing the risks of startup failures.

This small change has no impact on apps already ported to systemd, and will not worsten the experience of those who use rc-local, but will avoid an entire set of failure for those customers that still have to support legacy apps