Remove multiple SNO install complexity from SNO install playbooks

[akrzos]

Currently the SNO install playbooks allow you to install more than one SNO concurrently while the bare-metal playbook only installs one cluster at a time. I think we should reduce complexity of the SNO install playbooks to match the same structure as bare-metal install playbooks. If you want to install a second SNO, the user needs to actively manage their inventory file either by comment/uncommenting SNOs or creating additional inventory files. What do you think? @Noreen21 and @sferlin

[Noreen21]

I am in two minds about this issue. Even though I understand that this would help get the structure aligned with bare metal installments, the ability to be able to install multiple SNOs simultaneously without majorly tweaking anything is of great value to me (and hopefully others). It majorly reduces the environment build time when installing and applying all DU configs on multiple SNOs. The only drawback being that haproxy support is currently limited to only a single SNO from bastion, which can be overcome by use of ssh tunnels, so documenting this solution for when managing multiple SNOs from a single bastion would make life easier.

[akrzos]

Part of this issue was completed with #499, there is still more work to do to converge the sno deployment into mno so they can share more roles and common tasks etc.