Collation's propagate() function is used to check whether a constant string
can be propagated. Currently what we do is to check whether a collation has
contractions or expansions. But the propagate() function simply returns
false for each UCA collation, without regard to whether it really contains
contraction or expansion.

Fix:
Make UCA collation's propagate() function return proper value.

Change-Id: If4e63a2d62b309a58dfc2dfcfb4fc5e797f1b77d