High: parse: Fix resource sets, once and for all (savannah#41617)
The implicit value of both sequential and require-all is always
"true" in Pacemaker. The crmsh syntax for resource sets has different
implied values for these attributes depending on subtle changes in
syntax.

This commit tries to sort out the behavior of resource sets in crmsh
once and for all, and to document that behavior clearly in a single
location.