This bug was initially created as a copy of Bug #1465829

I am copying this bug because:
Initially, this feature should have been implemented in web UI as well, as mentioned in bz1465829 comment 1, but was done only for CLI. This clone is to cover the GUI part.

Unfortunately, [bug 1158500] missed this guidance point completely
(also because the effect of utilization was never properly tested?).

When setting utilization attribute while the placement-strategy is
"default" (implicitly or not) ...

1. ... on-the-fly: emit guidance message that placement-strategy cluster
property needs to be changed for the current change to take effect

2. ... accumulate + push: ditto as for 1. + make the "grand check"
in the push stage that will verify that the final CIB indeed
carries placement-strategy set to non-default, if not, emit
the warning once more + perhaps prevent the push unless --force
is specified

Note also there's no restriction of available values for
placement-strategy values in the current code.

References:
http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Pacemaker_Explained/index.html#_placement_strategy