OCF's tunnel vision regarding fully isolated runs of the agents (not the case in practice)

Observing recently as of now unpreventable configuration error:

https://github.com/ClusterLabs/pcs/issues/197

made me think how can we fix these undesirable shortcomings in our
cluster stack.

Borrowing from conclusion
https://github.com/ClusterLabs/pcs/issues/197#issuecomment-473529216:

> It's more a wider systemic flaw of never genuinely considering
> consequences of:
>
> 1. running semantically-matching instances of the agent in parallel
>
> 2. not preventing some patterns of agents' usage, or conversely,
> not enforcing some constraints to be used unconditionally for
> the configuration to be allowed
>
> To untwist it, we probably need a top-down approach, hence stating
> the expectations clearly in the OCF standard, as proposed for 1.

Complicated semantics of `mount` is exactly one such example where both
aspects shall be covered in the standard expressly:

1. possible intertwisting of different parameter sets agent instances
on `stop` operation (and perhaps elsewhere)

2. for `bind` mount points, there could be a way to arrange for
"last to leave the resource will trigger full-fledged stop", i.e.,
a concept built over an enforced _uniform_ (stop order the exact
inverse of start order) ordering of the `bind` instance to be
fully inside the life-time of the other managed mount point it
happens to delegate further (`bind` mount point would always
had to be stacked under true `mount`, borrowing its target path
as its own source path, never umounting on `stop`)

For 1., the standard shall be clear on the precautions agents are
meant to take to assure the general sanity:

see the proposal
https://github.com/ClusterLabs/resource-agents/issues/1304#issuecomment-473522631
and also the requirement on the resource manager to explicitly
avoid parallel executions of the same-parameter-sets (subject to
definition) instances

For 2., the metadata-level way of expressing "combinability" (stackability)
of the agents shall be devised. Prior art in rgmanager can be a useful
source of inspiration.