Feature: libpe_status,libpe_rules: drop support for default-resource-stickiness

... deprecated cluster property, along with its alias
default_resource_stickiness. Also, update affected regression tests and
documentation.

This results in one change in behavior. Previously (apparently due to a bug),
clones would ignore default-resource-stickiness, and use a default stickiness
of 1 if no resource-stickiness were set for the clone. However, they did (and
still do) honor resource-stickiness in rsc_defaults (and still use a default of
1 if nothing is specified there, either).