rpc_binder: weigh sending a message to a TA more heavily in `trusty_tipc_fuzzer`

Instead of equally weighing
1. adding a new TA
2. removing a TA
3. sending a message to a TA
weigh 3. more heavily, 20%-20%-60% so that
more time is spent fuzzing sending actual messages.

Test: build.py qemu-generic-arm64-fuzz-test-debug &&
    ./build-root/build-qemu-generic-arm64-fuzz-test-debug/run.py &&
    lunch qemu_trusty_arm64-trunk_staging-userdebug &&
    m trusty_binder_fuzzer_multi_connection &&
    adb root &&
    adb sync data &&
    adb shell /data/fuzz/arm64/trusty_binder_fuzzer_multi_connection/trusty_binder_fuzzer_multi_connection

Change-Id: I5a24fef059ded2a706d5c9229469f89ce90d6c5e
1 file changed