Use RavenwoodRule for system properties

We're going to remove RavenwoodConfig and will start using
RavenwoodRule (again) for initializing sysprops.

The "no RavenwoodRule" check in setUp() was stale, so just removed it.

Flag: EXEMPT host test change only
Bug: 377765941
Test: $ANDROID_BUILD_TOP/frameworks/base/ravenwood/scripts/run-ravenwood-tests.sh -t -s
Change-Id: Ic3406b7694f167cf415b58e05e220832f54d869c