Remove useless calls to xsnd

[AlexITC]

There are some unnecessary calls on the XSNService.

Expected behavior

There shouldn't be unnecessary calls.

Actual behavior

After the segwit integration, the addressindex was removed, leading to some useless calls on the XSNService, remove them:

def getAddressBalance(address: Address): FutureApplicationResult[rpc.AddressBalance]

def getTransactions(address: Address): FutureApplicationResult[List[TransactionId]]