Remove legacy-flow no-op variables: max, realMax and realProgress

Legacy onProgress aidl listener callback function used to take 2 params:
progress and max. So, the client had to calculate the percentage
progress. This legacy onProgress method is removed.

Now dumpstate sends the actual progress in percentage without requiring
the client to calculate it.

Bug: 123617758
Test: Takes interactive bugreport as expected. And shows progress
notification as expected.

Change-Id: Ic5a355cc886e51b964f73c227f5f657173e99420