[Pacemaker] Two resource nodes + one quorum node

[Nikita Staroverov]

> Its certainly possible to build a decent 2-node cluster, but there are 
> several non-obvious steps that are required - preventing fencing loops 
> being one. For this reason I cannot recommend them for newcomers, 
> because they are also the most likely group to be unaware of the caveats.
I think it's not so difficult. There are only two fine points, imho.
First, manual cluster services starting.
Second, avoiding fence race in split brain situations by adding in fence 
agent random action timeout which is big enough.