Revert "Restricted the workaround key to only cases where we aren't creating a"

This reverts commit fb66042cd3541aa21304936dc609b43c6ec38ac7.
Revert "Revert "Remove workaround for fast catchup""

This reverts commit 83be9eca1a8b512d2e06a812c6fd32905b3281fb.
Use HDAddress.EPOCH every time for the keys

This way, we don't need a workaround key.
Set the PeerGroup to scan only from scanTime on

Also set the BloomFilterFalsePositiveRate to a small value while rescanning
the whole blockchain, otherwise the Bloom filter is recalculated way too often.
Commented out altering of bloom filter false positive rate pending
further consideration.
Merge branch 'haraldh-noworkaround'